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	$193.94	8.375%	$210.1825	$210.18	$210.20	$210.20
Purchase #2	$84.84	6.836%	$90.6397	$90.64	$90.65	$90.60
Purchase #3	$17.85	5.342%	$18.8035	$18.80	$18.80	$18.80
Purchase #4	$108.63	11.254%	$120.8552	$120.86	$120.85	$120.90
Purchase #5	$232.75	7.794%	$250.8905	$250.89	$250.90	$250.90
Purchase #6	$248.82	6.112%	$264.0279	$264.03	$264.05	$264.00
Purchase #7	$175.77	10.773%	$194.7057	$194.71	$194.70	$194.70
7 purchase totals =	$1,062.60		$1,150.1050	$1,150.11	$1,150.15	$1,150.10