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	$204.67	13.108%	$231.4981	$231.50	$231.50	$231.50
Purchase #2	$167.48	12.132%	$187.7987	$187.80	$187.80	$187.80
Purchase #3	$97.57	4.172%	$101.6406	$101.64	$101.65	$101.60
Purchase #4	$63.59	6.701%	$67.8512	$67.85	$67.85	$67.90
Purchase #5	$37.96	12.766%	$42.806	$42.81	$42.80	$42.80
Purchase #6	$152.42	8.511%	$165.3925	$165.39	$165.40	$165.40
Purchase #7	$211.79	5.324%	$223.0657	$223.07	$223.05	$223.10
7 purchase totals =	$935.48		$1,020.0528	$1,020.06	$1,020.05	$1,020.10