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	$160.64	3.450%	$166.1821	$166.18	$166.20	$166.20
Purchase #2	$190.33	3.486%	$196.9649	$196.96	$196.95	$197.00
Purchase #3	$235.50	12.463%	$264.8504	$264.85	$264.85	$264.90
Purchase #4	$103.48	13.278%	$117.2201	$117.22	$117.20	$117.20
Purchase #5	$69.83	6.505%	$74.3724	$74.37	$74.35	$74.40
Purchase #6	$33.54	11.587%	$37.4263	$37.43	$37.45	$37.40
Purchase #7	$198.50	11.632%	$221.5895	$221.59	$221.60	$221.60
7 purchase totals =	$991.82		$1,078.6057	$1,078.60	$1,078.60	$1,078.70