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	$137.42	10.719%	$152.15	$152.15	$152.15	$152.20
Purchase #2	$195.73	12.173%	$219.5562	$219.56	$219.55	$219.60
Purchase #3	$242.25	5.538%	$255.6658	$255.67	$255.65	$255.70
Purchase #4	$169.30	10.429%	$186.9563	$186.96	$186.95	$187.00
Purchase #5	$139.65	12.412%	$156.9834	$156.98	$157.00	$157.00
Purchase #6	$51.83	4.398%	$54.1095	$54.11	$54.10	$54.10
Purchase #7	$134.31	13.527%	$152.4781	$152.48	$152.50	$152.50
7 purchase totals =	$1,070.49		$1,177.8993	$1,177.91	$1,177.90	$1,178.10