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	$146.30	4.223%	$152.4782	$152.48	$152.50	$152.50
Purchase #2	$5.54	12.412%	$6.2276	$6.23	$6.25	$6.20
Purchase #3	$55.71	9.809%	$61.1746	$61.17	$61.15	$61.20
Purchase #4	$67.52	10.453%	$74.5779	$74.58	$74.60	$74.60
Purchase #5	$11.74	11.518%	$13.0922	$13.09	$13.10	$13.10
Purchase #6	$57.42	7.542%	$61.7506	$61.75	$61.75	$61.80
Purchase #7	$54.38	13.819%	$61.8948	$61.89	$61.90	$61.90
7 purchase totals =	$398.61		$431.1959	$431.19	$431.25	$431.30