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	$37.50	9.281%	$40.9804	$40.98	$41.00	$41.00
Purchase #2	$111.82	3.232%	$115.434	$115.43	$115.45	$115.40
Purchase #3	$159.39	7.530%	$171.3921	$171.39	$171.40	$171.40
Purchase #4	$30.34	9.762%	$33.3018	$33.30	$33.30	$33.30
Purchase #5	$184.78	8.470%	$200.4309	$200.43	$200.45	$200.40
Purchase #6	$157.59	12.628%	$177.4905	$177.49	$177.50	$177.50
Purchase #7	$33.44	13.219%	$37.8604	$37.86	$37.85	$37.90
7 purchase totals =	$714.86		$776.8901	$776.88	$776.95	$776.90