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	$99.44	11.756%	$111.1302	$111.13	$111.15	$111.10
Purchase #2	$48.48	13.489%	$55.0195	$55.02	$55.00	$55.00
Purchase #3	$215.29	4.213%	$224.3602	$224.36	$224.35	$224.40
Purchase #4	$193.87	11.580%	$216.3201	$216.32	$216.30	$216.30
Purchase #5	$64.53	10.326%	$71.1934	$71.19	$71.20	$71.20
Purchase #6	$61.80	6.380%	$65.7428	$65.74	$65.75	$65.70
Purchase #7	$13.28	10.814%	$14.7161	$14.72	$14.70	$14.70
7 purchase totals =	$696.69		$758.4823	$758.48	$758.45	$758.40