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	$185.52	10.239%	$204.5154	$204.52	$204.50	$204.50
Purchase #2	$116.39	3.362%	$120.303	$120.30	$120.30	$120.30
Purchase #3	$169.28	9.108%	$184.698	$184.70	$184.70	$184.70
Purchase #4	$36.92	10.681%	$40.8634	$40.86	$40.85	$40.90
Purchase #5	$196.54	10.565%	$217.3045	$217.30	$217.30	$217.30
Purchase #6	$32.78	13.621%	$37.245	$37.25	$37.25	$37.20
Purchase #7	$211.55	13.841%	$240.8306	$240.83	$240.85	$240.80
7 purchase totals =	$948.98		$1,045.7599	$1,045.76	$1,045.75	$1,045.70