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	$184.72	13.344%	$209.369	$209.37	$209.35	$209.40
Purchase #2	$89.65	5.410%	$94.5001	$94.50	$94.50	$94.50
Purchase #3	$120.31	3.240%	$124.208	$124.21	$124.20	$124.20
Purchase #4	$180.79	10.773%	$200.2665	$200.27	$200.25	$200.30
Purchase #5	$214.44	10.328%	$236.5874	$236.59	$236.60	$236.60
Purchase #6	$215.92	3.680%	$223.8659	$223.87	$223.85	$223.90
Purchase #7	$77.37	11.856%	$86.543	$86.54	$86.55	$86.50
7 purchase totals =	$1,083.20		$1,175.3399	$1,175.35	$1,175.30	$1,175.40