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	$91.52	10.684%	$101.298	$101.30	$101.30	$101.30
Purchase #2	$210.66	10.805%	$233.4218	$233.42	$233.40	$233.40
Purchase #3	$135.36	4.414%	$141.3348	$141.33	$141.35	$141.30
Purchase #4	$201.68	4.472%	$210.6991	$210.70	$210.70	$210.70
Purchase #5	$87.81	3.532%	$90.9114	$90.91	$90.90	$90.90
Purchase #6	$98.75	13.261%	$111.8452	$111.85	$111.85	$111.80
Purchase #7	$149.88	5.735%	$158.4756	$158.48	$158.50	$158.50
7 purchase totals =	$975.66		$1,047.9859	$1,047.99	$1,048.00	$1,047.90