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	$19.54	12.687%	$22.019	$22.02	$22.00	$22.00
Purchase #2	$172.29	4.544%	$180.1189	$180.12	$180.10	$180.10
Purchase #3	$54.87	7.669%	$59.078	$59.08	$59.10	$59.10
Purchase #4	$234.49	12.549%	$263.9162	$263.92	$263.90	$263.90
Purchase #5	$165.66	5.343%	$174.5112	$174.51	$174.50	$174.50
Purchase #6	$76.45	4.595%	$79.9629	$79.96	$79.95	$80.00
Purchase #7	$177.54	10.594%	$196.3486	$196.35	$196.35	$196.30
7 purchase totals =	$900.84		$975.9548	$975.96	$975.90	$975.90