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	$181.25	4.732%	$189.8268	$189.83	$189.85	$189.80
Purchase #2	$57.73	8.700%	$62.7525	$62.75	$62.75	$62.80
Purchase #3	$44.28	3.260%	$45.7235	$45.72	$45.70	$45.70
Purchase #4	$72.48	6.601%	$77.2644	$77.26	$77.25	$77.30
Purchase #5	$38.48	5.425%	$40.5675	$40.57	$40.55	$40.60
Purchase #6	$223.73	11.175%	$248.7318	$248.73	$248.75	$248.70
Purchase #7	$58.44	13.774%	$66.4895	$66.49	$66.50	$66.50
7 purchase totals =	$676.39		$731.3560	$731.35	$731.35	$731.40