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	$249.88	5.618%	$263.9183	$263.92	$263.90	$263.90
Purchase #2	$217.95	7.745%	$234.8302	$234.83	$234.85	$234.80
Purchase #3	$152.29	11.872%	$170.3699	$170.37	$170.35	$170.40
Purchase #4	$172.26	11.264%	$191.6634	$191.66	$191.65	$191.70
Purchase #5	$63.38	13.773%	$72.1093	$72.11	$72.10	$72.10
Purchase #6	$158.98	4.386%	$165.9529	$165.95	$165.95	$166.00
Purchase #7	$103.68	7.399%	$111.3513	$111.35	$111.35	$111.40
7 purchase totals =	$1,118.42		$1,210.1953	$1,210.19	$1,210.15	$1,210.30