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	$201.70	10.335%	$222.5457	$222.55	$222.55	$222.50
Purchase #2	$40.54	6.462%	$43.1597	$43.16	$43.15	$43.20
Purchase #3	$104.75	9.315%	$114.5075	$114.51	$114.50	$114.50
Purchase #4	$99.58	5.210%	$104.7681	$104.77	$104.75	$104.80
Purchase #5	$158.82	8.419%	$172.1911	$172.19	$172.20	$172.20
Purchase #6	$131.52	6.667%	$140.2884	$140.29	$140.30	$140.30
Purchase #7	$223.82	9.390%	$244.8367	$244.84	$244.85	$244.80
7 purchase totals =	$960.73		$1,042.2972	$1,042.31	$1,042.30	$1,042.30