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	$157.63	7.785%	$169.9015	$169.90	$169.90	$169.90
Purchase #2	$209.95	4.724%	$219.868	$219.87	$219.85	$219.90
Purchase #3	$39.53	7.147%	$42.3552	$42.36	$42.35	$42.40
Purchase #4	$85.91	12.404%	$96.5663	$96.57	$96.55	$96.60
Purchase #5	$222.81	9.441%	$243.8455	$243.85	$243.85	$243.80
Purchase #6	$174.82	8.706%	$190.0398	$190.04	$190.05	$190.00
Purchase #7	$71.98	6.344%	$76.5464	$76.55	$76.55	$76.50
7 purchase totals =	$962.63		$1,039.1227	$1,039.14	$1,039.10	$1,039.10