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	$120.64	10.446%	$133.2421	$133.24	$133.25	$133.20
Purchase #2	$43.60	11.333%	$48.5412	$48.54	$48.55	$48.50
Purchase #3	$16.97	7.367%	$18.2202	$18.22	$18.20	$18.20
Purchase #4	$10.88	9.648%	$11.9297	$11.93	$11.95	$11.90
Purchase #5	$187.60	13.801%	$213.4907	$213.49	$213.50	$213.50
Purchase #6	$28.31	4.790%	$29.666	$29.67	$29.65	$29.70
Purchase #7	$154.51	11.466%	$172.2261	$172.23	$172.25	$172.20
7 purchase totals =	$562.51		$627.3160	$627.32	$627.35	$627.20