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	$67.32	7.676%	$72.4875	$72.49	$72.50	$72.50
Purchase #2	$137.25	6.668%	$146.4018	$146.40	$146.40	$146.40
Purchase #3	$5.98	12.476%	$6.7261	$6.73	$6.75	$6.70
Purchase #4	$209.51	9.409%	$229.2228	$229.22	$229.20	$229.20
Purchase #5	$54.67	11.841%	$61.1435	$61.14	$61.15	$61.10
Purchase #6	$238.89	11.815%	$267.1149	$267.11	$267.10	$267.10
Purchase #7	$229.75	13.815%	$261.49	$261.49	$261.50	$261.50
7 purchase totals =	$943.37		$1,044.5866	$1,044.58	$1,044.60	$1,044.50