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	$33.35	12.621%	$37.5591	$37.56	$37.55	$37.60
Purchase #2	$179.44	7.366%	$192.6576	$192.66	$192.65	$192.70
Purchase #3	$240.44	12.225%	$269.8338	$269.83	$269.85	$269.80
Purchase #4	$180.40	5.852%	$190.957	$190.96	$190.95	$191.00
Purchase #5	$83.67	13.837%	$95.2474	$95.25	$95.25	$95.20
Purchase #6	$90.37	10.242%	$99.6257	$99.63	$99.65	$99.60
Purchase #7	$160.45	7.145%	$171.9142	$171.91	$171.90	$171.90
7 purchase totals =	$968.12		$1,057.7948	$1,057.80	$1,057.80	$1,057.80