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	$41.67	5.441%	$43.9373	$43.94	$43.95	$43.90
Purchase #2	$222.30	11.485%	$247.8312	$247.83	$247.85	$247.80
Purchase #3	$112.25	11.197%	$124.8186	$124.82	$124.80	$124.80
Purchase #4	$174.91	6.295%	$185.9206	$185.92	$185.90	$185.90
Purchase #5	$221.41	8.448%	$240.1147	$240.11	$240.10	$240.10
Purchase #6	$231.32	9.675%	$253.7002	$253.70	$253.70	$253.70
Purchase #7	$53.98	9.427%	$59.0687	$59.07	$59.05	$59.10
7 purchase totals =	$1,057.84		$1,155.3913	$1,155.39	$1,155.35	$1,155.30