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	$100.52	8.331%	$108.8943	$108.89	$108.90	$108.90
Purchase #2	$174.56	11.300%	$194.2853	$194.29	$194.30	$194.30
Purchase #3	$42.74	8.410%	$46.3344	$46.33	$46.35	$46.30
Purchase #4	$233.59	7.602%	$251.3475	$251.35	$251.35	$251.30
Purchase #5	$95.56	5.331%	$100.6543	$100.65	$100.65	$100.70
Purchase #6	$59.85	3.865%	$62.1632	$62.16	$62.15	$62.20
Purchase #7	$245.82	4.532%	$256.9606	$256.96	$256.95	$257.00
7 purchase totals =	$952.64		$1,020.6396	$1,020.63	$1,020.65	$1,020.70