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	$162.96	13.529%	$185.0069	$185.01	$185.00	$185.00
Purchase #2	$134.38	13.360%	$152.3332	$152.33	$152.35	$152.30
Purchase #3	$179.43	8.328%	$194.3729	$194.37	$194.35	$194.40
Purchase #4	$21.79	4.855%	$22.8479	$22.85	$22.85	$22.80
Purchase #5	$82.71	12.390%	$92.9578	$92.96	$92.95	$93.00
Purchase #6	$6.72	4.872%	$7.0474	$7.05	$7.05	$7.00
Purchase #7	$148.61	3.117%	$153.2422	$153.24	$153.25	$153.20
7 purchase totals =	$736.60		$807.8083	$807.81	$807.80	$807.70