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	$190.97	3.154%	$196.9932	$196.99	$197.00	$197.00
Purchase #2	$244.70	6.467%	$260.5247	$260.52	$260.50	$260.50
Purchase #3	$211.88	9.326%	$231.6399	$231.64	$231.65	$231.60
Purchase #4	$249.72	12.347%	$280.5529	$280.55	$280.55	$280.60
Purchase #5	$119.36	4.550%	$124.7909	$124.79	$124.80	$124.80
Purchase #6	$113.96	11.874%	$127.4916	$127.49	$127.50	$127.50
Purchase #7	$30.94	5.175%	$32.5411	$32.54	$32.55	$32.50
7 purchase totals =	$1,161.53		$1,254.5343	$1,254.52	$1,254.55	$1,254.50