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	$145.61	8.823%	$158.4572	$158.46	$158.45	$158.50
Purchase #2	$17.89	10.819%	$19.8255	$19.83	$19.85	$19.80
Purchase #3	$221.78	3.372%	$229.2584	$229.26	$229.25	$229.30
Purchase #4	$109.45	4.438%	$114.3074	$114.31	$114.30	$114.30
Purchase #5	$66.47	13.528%	$75.4621	$75.46	$75.45	$75.50
Purchase #6	$184.79	6.428%	$196.6683	$196.67	$196.65	$196.70
Purchase #7	$88.35	7.706%	$95.1583	$95.16	$95.15	$95.20
7 purchase totals =	$834.34		$889.1372	$889.15	$889.10	$889.30