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	$186.43	4.866%	$195.5017	$195.50	$195.50	$195.50
Purchase #2	$6.50	13.854%	$7.4005	$7.40	$7.40	$7.40
Purchase #3	$209.83	10.294%	$231.4299	$231.43	$231.45	$231.40
Purchase #4	$85.84	4.338%	$89.5637	$89.56	$89.55	$89.60
Purchase #5	$127.59	7.364%	$136.9857	$136.99	$137.00	$137.00
Purchase #6	$86.48	8.355%	$93.7054	$93.71	$93.70	$93.70
Purchase #7	$42.79	4.127%	$44.5559	$44.56	$44.55	$44.60
7 purchase totals =	$745.46		$799.1428	$799.15	$799.15	$799.20