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	$232.47	4.258%	$242.3686	$242.37	$242.35	$242.40
Purchase #2	$88.89	12.859%	$100.3204	$100.32	$100.30	$100.30
Purchase #3	$199.95	4.639%	$209.2257	$209.23	$209.25	$209.20
Purchase #4	$111.32	11.487%	$124.1073	$124.11	$124.10	$124.10
Purchase #5	$113.53	4.528%	$118.6706	$118.67	$118.65	$118.70
Purchase #6	$109.75	8.542%	$119.1248	$119.12	$119.10	$119.10
Purchase #7	$143.40	5.251%	$150.9299	$150.93	$150.95	$150.90
7 purchase totals =	$999.31		$1,064.7473	$1,064.75	$1,064.70	$1,064.70