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	$110.55	8.760%	$120.2342	$120.23	$120.25	$120.20
Purchase #2	$39.47	11.755%	$44.1097	$44.11	$44.10	$44.10
Purchase #3	$215.58	3.165%	$222.4031	$222.40	$222.40	$222.40
Purchase #4	$86.50	3.399%	$89.4401	$89.44	$89.45	$89.40
Purchase #5	$237.91	5.659%	$251.3733	$251.37	$251.35	$251.40
Purchase #6	$186.41	5.179%	$196.0642	$196.06	$196.05	$196.10
Purchase #7	$225.35	10.295%	$248.5498	$248.55	$248.55	$248.50
7 purchase totals =	$1,101.77		$1,172.1744	$1,172.16	$1,172.15	$1,172.10