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	$37.69	13.820%	$42.8988	$42.90	$42.90	$42.90
Purchase #2	$90.28	6.489%	$96.1383	$96.14	$96.15	$96.10
Purchase #3	$56.46	9.453%	$61.7972	$61.80	$61.80	$61.80
Purchase #4	$118.55	4.656%	$124.0697	$124.07	$124.05	$124.10
Purchase #5	$12.30	7.382%	$13.208	$13.21	$13.20	$13.20
Purchase #6	$50.97	10.809%	$56.4793	$56.48	$56.50	$56.50
Purchase #7	$63.95	4.603%	$66.8936	$66.89	$66.90	$66.90
7 purchase totals =	$430.20		$461.4849	$461.49	$461.50	$461.50