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	$104.82	6.318%	$111.4425	$111.44	$111.45	$111.40
Purchase #2	$142.78	5.862%	$151.1498	$151.15	$151.15	$151.10
Purchase #3	$151.30	6.309%	$160.8455	$160.85	$160.85	$160.80
Purchase #4	$243.76	12.484%	$274.191	$274.19	$274.20	$274.20
Purchase #5	$70.94	8.475%	$76.9522	$76.95	$76.95	$77.00
Purchase #6	$221.94	4.736%	$232.4511	$232.45	$232.45	$232.50
Purchase #7	$55.98	5.146%	$58.8607	$58.86	$58.85	$58.90
7 purchase totals =	$991.52		$1,065.8928	$1,065.89	$1,065.90	$1,065.90