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	$99.98	5.262%	$105.2409	$105.24	$105.25	$105.20
Purchase #2	$57.70	4.217%	$60.1332	$60.13	$60.15	$60.10
Purchase #3	$144.49	6.125%	$153.34	$153.34	$153.35	$153.30
Purchase #4	$220.33	11.802%	$246.3333	$246.33	$246.35	$246.30
Purchase #5	$84.82	5.650%	$89.6123	$89.61	$89.60	$89.60
Purchase #6	$215.96	3.622%	$223.7821	$223.78	$223.80	$223.80
Purchase #7	$210.55	13.753%	$239.5069	$239.51	$239.50	$239.50
7 purchase totals =	$1,033.83		$1,117.9487	$1,117.94	$1,118.00	$1,117.80