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	$238.32	8.474%	$258.5152	$258.52	$258.50	$258.50
Purchase #2	$139.33	5.147%	$146.5013	$146.50	$146.50	$146.50
Purchase #3	$145.88	4.434%	$152.3483	$152.35	$152.35	$152.30
Purchase #4	$39.76	7.785%	$42.8553	$42.86	$42.85	$42.90
Purchase #5	$80.29	11.611%	$89.6125	$89.61	$89.60	$89.60
Purchase #6	$206.87	13.432%	$234.6568	$234.66	$234.65	$234.70
Purchase #7	$213.50	6.394%	$227.1512	$227.15	$227.15	$227.20
7 purchase totals =	$1,063.95		$1,151.6406	$1,151.65	$1,151.60	$1,151.70