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	$203.57	9.733%	$223.3835	$223.38	$223.40	$223.40
Purchase #2	$90.91	11.214%	$101.1046	$101.10	$101.10	$101.10
Purchase #3	$215.61	11.538%	$240.4871	$240.49	$240.50	$240.50
Purchase #4	$68.28	7.491%	$73.3949	$73.39	$73.40	$73.40
Purchase #5	$170.79	11.858%	$191.0423	$191.04	$191.05	$191.00
Purchase #6	$159.96	5.243%	$168.3467	$168.35	$168.35	$168.30
Purchase #7	$41.82	8.766%	$45.4859	$45.49	$45.50	$45.50
7 purchase totals =	$950.94		$1,043.2450	$1,043.24	$1,043.30	$1,043.20