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	$41.60	6.375%	$44.252	$44.25	$44.25	$44.30
Purchase #2	$136.72	11.272%	$152.1311	$152.13	$152.15	$152.10
Purchase #3	$52.70	4.229%	$54.9287	$54.93	$54.95	$54.90
Purchase #4	$226.46	7.738%	$243.9835	$243.98	$244.00	$244.00
Purchase #5	$67.65	6.244%	$71.8741	$71.87	$71.85	$71.90
Purchase #6	$238.94	12.383%	$268.5279	$268.53	$268.55	$268.50
Purchase #7	$33.51	11.244%	$37.2779	$37.28	$37.30	$37.30
7 purchase totals =	$797.58		$872.9752	$872.97	$873.05	$873.00