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	$69.29	11.865%	$77.5113	$77.51	$77.50	$77.50
Purchase #2	$130.89	8.767%	$142.3651	$142.37	$142.35	$142.40
Purchase #3	$242.82	5.660%	$256.5636	$256.56	$256.55	$256.60
Purchase #4	$193.54	3.651%	$200.6061	$200.61	$200.60	$200.60
Purchase #5	$38.72	5.424%	$40.8202	$40.82	$40.80	$40.80
Purchase #6	$240.51	11.229%	$267.5169	$267.52	$267.50	$267.50
Purchase #7	$49.40	8.419%	$53.559	$53.56	$53.55	$53.60
7 purchase totals =	$965.17		$1,038.9422	$1,038.95	$1,038.85	$1,039.00