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	$91.75	13.235%	$103.8931	$103.89	$103.90	$103.90
Purchase #2	$184.65	4.601%	$193.1457	$193.15	$193.15	$193.10
Purchase #3	$228.52	4.505%	$238.8148	$238.81	$238.80	$238.80
Purchase #4	$186.29	12.604%	$209.77	$209.77	$209.75	$209.80
Purchase #5	$57.80	8.686%	$62.8205	$62.82	$62.80	$62.80
Purchase #6	$35.59	5.294%	$37.4741	$37.47	$37.45	$37.50
Purchase #7	$87.41	13.264%	$99.0041	$99.00	$99.00	$99.00
7 purchase totals =	$872.01		$944.9223	$944.91	$944.85	$944.90