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	$181.26	9.586%	$198.6356	$198.64	$198.65	$198.60
Purchase #2	$93.35	6.589%	$99.5008	$99.50	$99.50	$99.50
Purchase #3	$11.86	3.197%	$12.2392	$12.24	$12.25	$12.20
Purchase #4	$42.27	8.573%	$45.8938	$45.89	$45.90	$45.90
Purchase #5	$242.39	10.547%	$267.9549	$267.95	$267.95	$268.00
Purchase #6	$51.58	8.195%	$55.807	$55.81	$55.80	$55.80
Purchase #7	$203.74	12.680%	$229.5742	$229.57	$229.55	$229.60
7 purchase totals =	$826.45		$909.6055	$909.60	$909.60	$909.60