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	$194.41	9.197%	$212.2899	$212.29	$212.30	$212.30
Purchase #2	$182.74	6.648%	$194.8886	$194.89	$194.90	$194.90
Purchase #3	$191.53	13.356%	$217.1107	$217.11	$217.10	$217.10
Purchase #4	$93.66	13.142%	$105.9688	$105.97	$105.95	$106.00
Purchase #5	$92.49	13.530%	$105.0039	$105.00	$105.00	$105.00
Purchase #6	$77.80	6.226%	$82.6438	$82.64	$82.65	$82.60
Purchase #7	$181.47	10.388%	$200.3211	$200.32	$200.30	$200.30
7 purchase totals =	$1,014.10		$1,118.2268	$1,118.22	$1,118.20	$1,118.20