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	$75.53	10.533%	$83.4856	$83.49	$83.50	$83.50
Purchase #2	$159.73	8.152%	$172.7512	$172.75	$172.75	$172.80
Purchase #3	$81.81	10.117%	$90.0867	$90.09	$90.10	$90.10
Purchase #4	$182.95	9.588%	$200.4912	$200.49	$200.50	$200.50
Purchase #5	$162.36	13.719%	$184.6342	$184.63	$184.65	$184.60
Purchase #6	$98.80	10.582%	$109.255	$109.26	$109.25	$109.30
Purchase #7	$200.56	7.810%	$216.2237	$216.22	$216.20	$216.20
7 purchase totals =	$961.74		$1,056.9276	$1,056.93	$1,056.95	$1,057.00