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	$17.74	9.234%	$19.3781	$19.38	$19.40	$19.40
Purchase #2	$170.95	12.406%	$192.1581	$192.16	$192.15	$192.20
Purchase #3	$246.59	13.265%	$279.3002	$279.30	$279.30	$279.30
Purchase #4	$174.50	12.341%	$196.035	$196.04	$196.05	$196.00
Purchase #5	$194.71	4.725%	$203.91	$203.91	$203.90	$203.90
Purchase #6	$94.63	4.359%	$98.7549	$98.75	$98.75	$98.80
Purchase #7	$25.51	13.266%	$28.8942	$28.89	$28.90	$28.90
7 purchase totals =	$924.63		$1,018.4305	$1,018.43	$1,018.45	$1,018.50