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	$40.79	10.366%	$45.0183	$45.02	$45.00	$45.00
Purchase #2	$114.33	4.383%	$119.3411	$119.34	$119.35	$119.30
Purchase #3	$57.98	13.413%	$65.7569	$65.76	$65.75	$65.80
Purchase #4	$228.95	7.763%	$246.7234	$246.72	$246.70	$246.70
Purchase #5	$128.77	10.575%	$142.3874	$142.39	$142.40	$142.40
Purchase #6	$179.95	7.255%	$193.0054	$193.01	$193.00	$193.00
Purchase #7	$100.96	10.208%	$111.266	$111.27	$111.25	$111.30
7 purchase totals =	$851.73		$923.4985	$923.51	$923.45	$923.50