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	$40.33	9.104%	$44.0016	$44.00	$44.00	$44.00
Purchase #2	$239.63	6.647%	$255.5582	$255.56	$255.55	$255.60
Purchase #3	$33.80	10.573%	$37.3737	$37.37	$37.35	$37.40
Purchase #4	$11.73	3.182%	$12.1032	$12.10	$12.10	$12.10
Purchase #5	$50.89	8.617%	$55.2752	$55.28	$55.30	$55.30
Purchase #6	$206.96	10.685%	$229.0737	$229.07	$229.05	$229.10
Purchase #7	$55.28	11.415%	$61.5902	$61.59	$61.60	$61.60
7 purchase totals =	$638.62		$694.9758	$694.97	$694.95	$695.10