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	$131.86	3.811%	$136.8852	$136.89	$136.90	$136.90
Purchase #2	$29.83	11.445%	$33.244	$33.24	$33.25	$33.20
Purchase #3	$141.53	10.159%	$155.908	$155.91	$155.90	$155.90
Purchase #4	$17.48	5.787%	$18.4916	$18.49	$18.50	$18.50
Purchase #5	$53.55	10.381%	$59.109	$59.11	$59.10	$59.10
Purchase #6	$176.64	5.282%	$185.9701	$185.97	$185.95	$186.00
Purchase #7	$19.54	5.260%	$20.5678	$20.57	$20.55	$20.60
7 purchase totals =	$570.43		$610.1757	$610.18	$610.15	$610.20