Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$176.48	5.681%	$186.5058	$186.51	$186.50	$186.50
Purchase #2	$200.62	5.446%	$211.5458	$211.55	$211.55	$211.50
Purchase #3	$207.96	10.499%	$229.7937	$229.79	$229.80	$229.80
Purchase #4	$165.46	4.357%	$172.6691	$172.67	$172.65	$172.70
Purchase #5	$246.89	8.275%	$267.3201	$267.32	$267.30	$267.30
Purchase #6	$250.39	12.147%	$280.8049	$280.80	$280.80	$280.80
Purchase #7	$172.89	3.587%	$179.0916	$179.09	$179.10	$179.10
7 purchase totals =	$1,420.69		$1,527.7310	$1,527.73	$1,527.70	$1,527.70