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	$184.65	3.196%	$190.5514	$190.55	$190.55	$190.60
Purchase #2	$124.30	3.309%	$128.4131	$128.41	$128.40	$128.40
Purchase #3	$148.58	13.572%	$168.7453	$168.75	$168.75	$168.70
Purchase #4	$166.40	11.267%	$185.1483	$185.15	$185.15	$185.10
Purchase #5	$36.90	4.676%	$38.6254	$38.63	$38.65	$38.60
Purchase #6	$137.57	12.170%	$154.3123	$154.31	$154.30	$154.30
Purchase #7	$147.75	3.206%	$152.4869	$152.49	$152.50	$152.50
7 purchase totals =	$946.15		$1,018.2827	$1,018.29	$1,018.30	$1,018.20