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	$220.29	12.138%	$247.0288	$247.03	$247.05	$247.00
Purchase #2	$104.29	7.697%	$112.3172	$112.32	$112.30	$112.30
Purchase #3	$227.58	9.790%	$249.8601	$249.86	$249.85	$249.90
Purchase #4	$145.36	12.746%	$163.8876	$163.89	$163.90	$163.90
Purchase #5	$189.64	3.653%	$196.5675	$196.57	$196.55	$196.60
Purchase #6	$47.60	6.244%	$50.5721	$50.57	$50.55	$50.60
Purchase #7	$84.70	13.208%	$95.8872	$95.89	$95.90	$95.90
7 purchase totals =	$1,019.46		$1,116.1205	$1,116.13	$1,116.10	$1,116.20