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	$133.43	11.310%	$148.5209	$148.52	$148.50	$148.50
Purchase #2	$36.94	13.328%	$41.8634	$41.86	$41.85	$41.90
Purchase #3	$176.50	9.275%	$192.8704	$192.87	$192.85	$192.90
Purchase #4	$78.58	9.640%	$86.1551	$86.16	$86.15	$86.20
Purchase #5	$239.76	13.210%	$271.4323	$271.43	$271.45	$271.40
Purchase #6	$97.64	13.458%	$110.7804	$110.78	$110.80	$110.80
Purchase #7	$247.51	9.792%	$271.7462	$271.75	$271.75	$271.70
7 purchase totals =	$1,010.36		$1,123.3687	$1,123.37	$1,123.35	$1,123.40