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	$148.52	12.272%	$166.7464	$166.75	$166.75	$166.70
Purchase #2	$99.72	12.729%	$112.4134	$112.41	$112.40	$112.40
Purchase #3	$151.33	5.538%	$159.7107	$159.71	$159.70	$159.70
Purchase #4	$46.86	11.853%	$52.4143	$52.41	$52.40	$52.40
Purchase #5	$174.68	12.462%	$196.4486	$196.45	$196.45	$196.40
Purchase #6	$39.29	3.615%	$40.7103	$40.71	$40.70	$40.70
Purchase #7	$86.83	13.339%	$98.4123	$98.41	$98.40	$98.40
7 purchase totals =	$747.23		$826.8560	$826.85	$826.80	$826.70