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	$49.46	4.835%	$51.8514	$51.85	$51.85	$51.90
Purchase #2	$230.93	10.756%	$255.7688	$255.77	$255.75	$255.80
Purchase #3	$185.40	7.573%	$199.4403	$199.44	$199.45	$199.40
Purchase #4	$41.90	6.251%	$44.5192	$44.52	$44.50	$44.50
Purchase #5	$35.94	8.785%	$39.0973	$39.10	$39.10	$39.10
Purchase #6	$242.35	8.741%	$263.5338	$263.53	$263.55	$263.50
Purchase #7	$155.98	9.795%	$171.2582	$171.26	$171.25	$171.30
7 purchase totals =	$941.96		$1,025.4690	$1,025.47	$1,025.45	$1,025.50