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	$155.94	3.609%	$161.5679	$161.57	$161.55	$161.60
Purchase #2	$250.63	7.150%	$268.55	$268.55	$268.55	$268.60
Purchase #3	$20.63	6.311%	$21.932	$21.93	$21.95	$21.90
Purchase #4	$243.50	5.200%	$256.162	$256.16	$256.15	$256.20
Purchase #5	$89.84	13.190%	$101.6899	$101.69	$101.70	$101.70
Purchase #6	$51.73	11.368%	$57.6107	$57.61	$57.60	$57.60
Purchase #7	$144.42	4.261%	$150.5737	$150.57	$150.55	$150.60
7 purchase totals =	$956.69		$1,018.0862	$1,018.08	$1,018.05	$1,018.20