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	$248.33	13.352%	$281.487	$281.49	$281.50	$281.50
Purchase #2	$33.33	9.601%	$36.53	$36.53	$36.55	$36.50
Purchase #3	$227.43	5.681%	$240.3503	$240.35	$240.35	$240.40
Purchase #4	$194.30	12.795%	$219.1607	$219.16	$219.15	$219.20
Purchase #5	$95.89	4.125%	$99.8455	$99.85	$99.85	$99.80
Purchase #6	$238.59	13.513%	$270.8307	$270.83	$270.85	$270.80
Purchase #7	$40.97	10.150%	$45.1285	$45.13	$45.15	$45.10
7 purchase totals =	$1,078.84		$1,193.3327	$1,193.34	$1,193.40	$1,193.30