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	$167.57	12.259%	$188.1124	$188.11	$188.10	$188.10
Purchase #2	$65.70	8.176%	$71.0716	$71.07	$71.05	$71.10
Purchase #3	$234.70	9.338%	$256.6163	$256.62	$256.60	$256.60
Purchase #4	$232.81	5.180%	$244.8696	$244.87	$244.85	$244.90
Purchase #5	$173.69	8.795%	$188.966	$188.97	$188.95	$189.00
Purchase #6	$55.33	7.127%	$59.2734	$59.27	$59.25	$59.30
Purchase #7	$147.25	5.675%	$155.6064	$155.61	$155.60	$155.60
7 purchase totals =	$1,077.05		$1,164.5157	$1,164.52	$1,164.40	$1,164.60