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	$39.69	4.723%	$41.5646	$41.56	$41.55	$41.60
Purchase #2	$245.72	13.717%	$279.4254	$279.43	$279.45	$279.40
Purchase #3	$180.72	3.150%	$186.4127	$186.41	$186.40	$186.40
Purchase #4	$200.91	11.207%	$223.426	$223.43	$223.45	$223.40
Purchase #5	$130.51	13.549%	$148.1928	$148.19	$148.20	$148.20
Purchase #6	$136.40	7.634%	$146.8128	$146.81	$146.80	$146.80
Purchase #7	$51.66	4.364%	$53.9144	$53.91	$53.90	$53.90
7 purchase totals =	$985.61		$1,079.7487	$1,079.74	$1,079.75	$1,079.70