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	$34.41	10.148%	$37.9019	$37.90	$37.90	$37.90
Purchase #2	$203.70	9.272%	$222.5871	$222.59	$222.60	$222.60
Purchase #3	$161.98	12.671%	$182.5045	$182.50	$182.50	$182.50
Purchase #4	$62.56	7.448%	$67.2195	$67.22	$67.20	$67.20
Purchase #5	$158.64	6.779%	$169.3942	$169.39	$169.40	$169.40
Purchase #6	$27.40	4.188%	$28.5475	$28.55	$28.55	$28.50
Purchase #7	$5.43	8.423%	$5.8874	$5.89	$5.90	$5.90
7 purchase totals =	$654.12		$714.0421	$714.04	$714.05	$714.00