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	$193.35	10.760%	$214.1545	$214.15	$214.15	$214.20
Purchase #2	$79.53	7.860%	$85.7811	$85.78	$85.80	$85.80
Purchase #3	$58.94	7.368%	$63.2827	$63.28	$63.30	$63.30
Purchase #4	$216.60	3.208%	$223.5485	$223.55	$223.55	$223.50
Purchase #5	$155.39	9.320%	$169.8723	$169.87	$169.85	$169.90
Purchase #6	$118.53	4.240%	$123.5557	$123.56	$123.55	$123.60
Purchase #7	$87.39	9.488%	$95.6816	$95.68	$95.70	$95.70
7 purchase totals =	$909.73		$975.8764	$975.87	$975.90	$976.00