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	$165.89	11.741%	$185.3671	$185.37	$185.35	$185.40
Purchase #2	$12.64	12.331%	$14.1986	$14.20	$14.20	$14.20
Purchase #3	$89.25	3.647%	$92.5049	$92.50	$92.50	$92.50
Purchase #4	$232.54	10.144%	$256.1289	$256.13	$256.15	$256.10
Purchase #5	$8.85	11.852%	$9.8989	$9.90	$9.90	$9.90
Purchase #6	$130.54	9.407%	$142.8199	$142.82	$142.80	$142.80
Purchase #7	$12.38	7.797%	$13.3453	$13.35	$13.35	$13.30
7 purchase totals =	$652.09		$714.2636	$714.27	$714.25	$714.20