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	$95.28	13.644%	$108.28	$108.28	$108.30	$108.30
Purchase #2	$22.96	5.586%	$24.2425	$24.24	$24.25	$24.20
Purchase #3	$78.44	8.809%	$85.3498	$85.35	$85.35	$85.30
Purchase #4	$81.96	11.574%	$91.4461	$91.45	$91.45	$91.40
Purchase #5	$37.57	11.639%	$41.9428	$41.94	$41.95	$41.90
Purchase #6	$88.42	8.233%	$95.6996	$95.70	$95.70	$95.70
Purchase #7	$98.69	13.829%	$112.3378	$112.34	$112.35	$112.30
7 purchase totals =	$503.32		$559.2986	$559.30	$559.35	$559.10