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	$214.82	3.717%	$222.8049	$222.80	$222.80	$222.80
Purchase #2	$234.87	8.653%	$255.1933	$255.19	$255.20	$255.20
Purchase #3	$177.28	3.874%	$184.1478	$184.15	$184.15	$184.10
Purchase #4	$147.75	13.640%	$167.9031	$167.90	$167.90	$167.90
Purchase #5	$174.62	11.387%	$194.504	$194.50	$194.50	$194.50
Purchase #6	$203.66	9.586%	$223.1828	$223.18	$223.20	$223.20
Purchase #7	$163.69	9.449%	$179.1571	$179.16	$179.15	$179.20
7 purchase totals =	$1,316.69		$1,426.8930	$1,426.88	$1,426.90	$1,426.90