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	$95.60	3.658%	$99.097	$99.10	$99.10	$99.10
Purchase #2	$196.84	5.740%	$208.1386	$208.14	$208.15	$208.10
Purchase #3	$250.52	12.494%	$281.82	$281.82	$281.80	$281.80
Purchase #4	$41.75	10.785%	$46.2527	$46.25	$46.25	$46.30
Purchase #5	$154.65	3.159%	$159.5354	$159.54	$159.55	$159.50
Purchase #6	$88.46	6.207%	$93.9507	$93.95	$93.95	$94.00
Purchase #7	$172.63	5.649%	$182.3819	$182.38	$182.40	$182.40
7 purchase totals =	$1,000.45		$1,071.1763	$1,071.18	$1,071.20	$1,071.20