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	$39.69	13.655%	$45.1097	$45.11	$45.10	$45.10
Purchase #2	$211.86	12.522%	$238.3891	$238.39	$238.40	$238.40
Purchase #3	$228.37	7.394%	$245.2557	$245.26	$245.25	$245.30
Purchase #4	$94.90	12.277%	$106.5509	$106.55	$106.55	$106.60
Purchase #5	$227.33	6.518%	$242.1474	$242.15	$242.15	$242.10
Purchase #6	$29.44	12.174%	$33.024	$33.02	$33.00	$33.00
Purchase #7	$132.85	13.268%	$150.4765	$150.48	$150.50	$150.50
7 purchase totals =	$964.44		$1,060.9533	$1,060.96	$1,060.95	$1,061.00