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	$144.38	8.836%	$157.1374	$157.14	$157.15	$157.10
Purchase #2	$182.98	13.713%	$208.072	$208.07	$208.05	$208.10
Purchase #3	$39.62	3.341%	$40.9437	$40.94	$40.95	$40.90
Purchase #4	$129.51	12.151%	$145.2468	$145.25	$145.25	$145.20
Purchase #5	$93.72	11.809%	$104.7874	$104.79	$104.80	$104.80
Purchase #6	$247.41	10.591%	$273.6132	$273.61	$273.60	$273.60
Purchase #7	$76.51	7.809%	$82.4847	$82.48	$82.50	$82.50
7 purchase totals =	$914.13		$1,012.2852	$1,012.28	$1,012.30	$1,012.20