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	$20.31	9.643%	$22.2685	$22.27	$22.25	$22.30
Purchase #2	$172.46	11.512%	$192.3136	$192.31	$192.30	$192.30
Purchase #3	$117.41	9.453%	$128.5088	$128.51	$128.50	$128.50
Purchase #4	$11.31	9.353%	$12.3678	$12.37	$12.35	$12.40
Purchase #5	$247.37	7.351%	$265.5542	$265.55	$265.55	$265.60
Purchase #6	$189.54	8.235%	$205.1486	$205.15	$205.15	$205.10
Purchase #7	$210.39	11.651%	$234.9025	$234.90	$234.90	$234.90
7 purchase totals =	$968.79		$1,061.0640	$1,061.06	$1,061.00	$1,061.10