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	$148.51	3.488%	$153.69	$153.69	$153.70	$153.70
Purchase #2	$40.61	8.610%	$44.1065	$44.11	$44.10	$44.10
Purchase #3	$174.69	4.841%	$183.1467	$183.15	$183.15	$183.10
Purchase #4	$39.56	4.435%	$41.3145	$41.31	$41.30	$41.30
Purchase #5	$212.25	13.422%	$240.7382	$240.74	$240.75	$240.70
Purchase #6	$6.87	9.468%	$7.5205	$7.52	$7.50	$7.50
Purchase #7	$38.43	12.256%	$43.14	$43.14	$43.15	$43.10
7 purchase totals =	$660.92		$713.6564	$713.66	$713.65	$713.50