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	$92.50	8.576%	$100.4328	$100.43	$100.45	$100.40
Purchase #2	$76.25	3.395%	$78.8387	$78.84	$78.85	$78.80
Purchase #3	$220.51	9.499%	$241.4562	$241.46	$241.45	$241.50
Purchase #4	$153.39	7.788%	$165.336	$165.34	$165.35	$165.30
Purchase #5	$234.92	10.360%	$259.2577	$259.26	$259.25	$259.30
Purchase #6	$72.87	3.824%	$75.6565	$75.66	$75.65	$75.70
Purchase #7	$199.95	11.595%	$223.1342	$223.13	$223.15	$223.10
7 purchase totals =	$1,050.39		$1,144.1121	$1,144.12	$1,144.15	$1,144.10