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	$163.85	11.159%	$182.134	$182.13	$182.15	$182.10
Purchase #2	$200.68	4.316%	$209.3413	$209.34	$209.35	$209.30
Purchase #3	$89.65	10.442%	$99.0113	$99.01	$99.00	$99.00
Purchase #4	$74.29	11.869%	$83.1075	$83.11	$83.10	$83.10
Purchase #5	$34.29	9.276%	$37.4707	$37.47	$37.45	$37.50
Purchase #6	$247.83	6.735%	$264.5214	$264.52	$264.50	$264.50
Purchase #7	$194.70	6.356%	$207.0751	$207.08	$207.10	$207.10
7 purchase totals =	$1,005.29		$1,082.6613	$1,082.66	$1,082.65	$1,082.60