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	$8.52	5.394%	$8.9796	$8.98	$9.00	$9.00
Purchase #2	$238.48	11.321%	$265.4783	$265.48	$265.50	$265.50
Purchase #3	$226.93	11.868%	$253.8621	$253.86	$253.85	$253.90
Purchase #4	$240.95	9.472%	$263.7728	$263.77	$263.75	$263.80
Purchase #5	$20.31	6.589%	$21.6482	$21.65	$21.65	$21.60
Purchase #6	$57.70	6.527%	$61.4661	$61.47	$61.45	$61.50
Purchase #7	$210.39	4.173%	$219.1696	$219.17	$219.15	$219.20
7 purchase totals =	$1,003.28		$1,094.3767	$1,094.38	$1,094.35	$1,094.50