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	$221.62	10.349%	$244.5555	$244.56	$244.55	$244.60
Purchase #2	$51.48	13.120%	$58.2342	$58.23	$58.25	$58.20
Purchase #3	$183.92	3.275%	$189.9434	$189.94	$189.95	$189.90
Purchase #4	$80.91	10.864%	$89.7001	$89.70	$89.70	$89.70
Purchase #5	$54.88	11.462%	$61.1703	$61.17	$61.15	$61.20
Purchase #6	$36.59	3.669%	$37.9325	$37.93	$37.95	$37.90
Purchase #7	$207.50	7.467%	$222.994	$222.99	$223.00	$223.00
7 purchase totals =	$836.90		$904.5300	$904.52	$904.55	$904.50