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	$91.66	9.402%	$100.2779	$100.28	$100.30	$100.30
Purchase #2	$146.72	9.251%	$160.2931	$160.29	$160.30	$160.30
Purchase #3	$84.26	6.707%	$89.9113	$89.91	$89.90	$89.90
Purchase #4	$103.46	3.438%	$107.017	$107.02	$107.00	$107.00
Purchase #5	$120.82	3.698%	$125.2879	$125.29	$125.30	$125.30
Purchase #6	$228.39	6.588%	$243.4363	$243.44	$243.45	$243.40
Purchase #7	$199.85	8.708%	$217.2529	$217.25	$217.25	$217.30
7 purchase totals =	$975.16		$1,043.4764	$1,043.48	$1,043.50	$1,043.50