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	$161.25	13.213%	$182.556	$182.56	$182.55	$182.60
Purchase #2	$77.35	11.633%	$86.3481	$86.35	$86.35	$86.30
Purchase #3	$56.28	9.762%	$61.7741	$61.77	$61.75	$61.80
Purchase #4	$75.40	3.634%	$78.14	$78.14	$78.15	$78.10
Purchase #5	$158.27	13.501%	$179.638	$179.64	$179.65	$179.60
Purchase #6	$159.54	12.304%	$179.1698	$179.17	$179.15	$179.20
Purchase #7	$79.87	7.813%	$86.1102	$86.11	$86.10	$86.10
7 purchase totals =	$767.96		$853.7362	$853.74	$853.70	$853.70