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	$165.82	5.188%	$174.4227	$174.42	$174.40	$174.40
Purchase #2	$229.29	11.728%	$256.1811	$256.18	$256.20	$256.20
Purchase #3	$64.34	3.479%	$66.5784	$66.58	$66.60	$66.60
Purchase #4	$201.88	3.779%	$209.509	$209.51	$209.50	$209.50
Purchase #5	$41.76	5.330%	$43.9858	$43.99	$44.00	$44.00
Purchase #6	$43.75	4.872%	$45.8815	$45.88	$45.90	$45.90
Purchase #7	$245.54	7.306%	$263.4792	$263.48	$263.50	$263.50
7 purchase totals =	$992.38		$1,060.0377	$1,060.04	$1,060.10	$1,060.10