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	$177.62	6.250%	$188.7213	$188.72	$188.70	$188.70
Purchase #2	$213.72	10.110%	$235.3271	$235.33	$235.35	$235.30
Purchase #3	$186.42	12.603%	$209.9145	$209.91	$209.90	$209.90
Purchase #4	$92.84	3.291%	$95.8954	$95.90	$95.90	$95.90
Purchase #5	$119.37	3.588%	$123.653	$123.65	$123.65	$123.70
Purchase #6	$36.80	10.588%	$40.6964	$40.70	$40.70	$40.70
Purchase #7	$243.88	12.468%	$274.287	$274.29	$274.30	$274.30
7 purchase totals =	$1,070.65		$1,168.4947	$1,168.50	$1,168.50	$1,168.50