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	$50.32	9.845%	$55.274	$55.27	$55.25	$55.30
Purchase #2	$26.30	4.459%	$27.4727	$27.47	$27.45	$27.50
Purchase #3	$204.51	11.689%	$228.4152	$228.42	$228.40	$228.40
Purchase #4	$193.54	9.516%	$211.9573	$211.96	$211.95	$212.00
Purchase #5	$152.33	8.417%	$165.1516	$165.15	$165.15	$165.20
Purchase #6	$105.98	5.614%	$111.9297	$111.93	$111.95	$111.90
Purchase #7	$248.81	6.650%	$265.3559	$265.36	$265.35	$265.40
7 purchase totals =	$981.79		$1,065.5564	$1,065.56	$1,065.50	$1,065.70