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	$76.63	6.387%	$81.5244	$81.52	$81.50	$81.50
Purchase #2	$77.38	6.182%	$82.1636	$82.16	$82.15	$82.20
Purchase #3	$240.58	9.268%	$262.877	$262.88	$262.90	$262.90
Purchase #4	$198.40	13.757%	$225.6939	$225.69	$225.70	$225.70
Purchase #5	$39.82	13.145%	$45.0543	$45.05	$45.05	$45.10
Purchase #6	$247.82	13.755%	$281.9076	$281.91	$281.90	$281.90
Purchase #7	$132.33	13.731%	$150.5002	$150.50	$150.50	$150.50
7 purchase totals =	$1,012.96		$1,129.7210	$1,129.71	$1,129.70	$1,129.80