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	$185.91	12.132%	$208.4646	$208.46	$208.45	$208.50
Purchase #2	$41.39	10.145%	$45.589	$45.59	$45.60	$45.60
Purchase #3	$154.54	13.700%	$175.712	$175.71	$175.70	$175.70
Purchase #4	$246.98	4.701%	$258.5905	$258.59	$258.60	$258.60
Purchase #5	$182.90	9.405%	$200.1017	$200.10	$200.10	$200.10
Purchase #6	$92.58	8.111%	$100.0892	$100.09	$100.10	$100.10
Purchase #7	$14.37	9.871%	$15.7885	$15.79	$15.80	$15.80
7 purchase totals =	$918.67		$1,004.3355	$1,004.33	$1,004.35	$1,004.40