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	$47.58	3.691%	$49.3362	$49.34	$49.35	$49.30
Purchase #2	$174.71	7.780%	$188.3024	$188.30	$188.30	$188.30
Purchase #3	$154.58	13.181%	$174.9552	$174.96	$174.95	$175.00
Purchase #4	$242.45	12.329%	$272.3417	$272.34	$272.35	$272.30
Purchase #5	$176.26	5.443%	$185.8538	$185.85	$185.85	$185.90
Purchase #6	$39.43	7.205%	$42.2709	$42.27	$42.25	$42.30
Purchase #7	$85.55	11.869%	$95.7039	$95.70	$95.70	$95.70
7 purchase totals =	$920.56		$1,008.7641	$1,008.76	$1,008.75	$1,008.80