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	$194.48	12.524%	$218.8367	$218.84	$218.85	$218.80
Purchase #2	$111.73	5.293%	$117.6439	$117.64	$117.65	$117.60
Purchase #3	$20.62	9.261%	$22.5296	$22.53	$22.55	$22.50
Purchase #4	$124.72	12.181%	$139.9121	$139.91	$139.90	$139.90
Purchase #5	$43.27	4.221%	$45.0964	$45.10	$45.10	$45.10
Purchase #6	$138.85	6.561%	$147.9599	$147.96	$147.95	$148.00
Purchase #7	$124.94	4.509%	$130.5735	$130.57	$130.55	$130.60
7 purchase totals =	$758.61		$822.5521	$822.55	$822.55	$822.50