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	$115.69	11.448%	$128.9342	$128.93	$128.95	$128.90
Purchase #2	$101.51	4.556%	$106.1348	$106.13	$106.15	$106.10
Purchase #3	$55.53	11.621%	$61.9831	$61.98	$62.00	$62.00
Purchase #4	$244.76	10.542%	$270.5626	$270.56	$270.55	$270.60
Purchase #5	$38.49	10.510%	$42.5353	$42.54	$42.55	$42.50
Purchase #6	$99.85	6.534%	$106.3742	$106.37	$106.35	$106.40
Purchase #7	$39.90	13.401%	$45.247	$45.25	$45.25	$45.20
7 purchase totals =	$695.73		$761.7712	$761.76	$761.80	$761.70