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	$230.33	10.717%	$255.0145	$255.01	$255.00	$255.00
Purchase #2	$18.41	9.173%	$20.0987	$20.10	$20.10	$20.10
Purchase #3	$167.96	10.119%	$184.9559	$184.96	$184.95	$185.00
Purchase #4	$228.61	8.287%	$247.5549	$247.55	$247.55	$247.60
Purchase #5	$156.41	4.573%	$163.5626	$163.56	$163.55	$163.60
Purchase #6	$48.26	13.149%	$54.6057	$54.61	$54.60	$54.60
Purchase #7	$90.88	9.668%	$99.6663	$99.67	$99.65	$99.70
7 purchase totals =	$940.86		$1,025.4586	$1,025.46	$1,025.40	$1,025.60