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	$244.67	3.655%	$253.6127	$253.61	$253.60	$253.60
Purchase #2	$205.34	5.276%	$216.1737	$216.17	$216.15	$216.20
Purchase #3	$125.54	4.210%	$130.8252	$130.83	$130.85	$130.80
Purchase #4	$175.74	7.621%	$189.1331	$189.13	$189.15	$189.10
Purchase #5	$36.94	13.814%	$42.0429	$42.04	$42.05	$42.00
Purchase #6	$137.73	4.421%	$143.819	$143.82	$143.80	$143.80
Purchase #7	$83.99	10.497%	$92.8064	$92.81	$92.80	$92.80
7 purchase totals =	$1,009.95		$1,068.4130	$1,068.41	$1,068.40	$1,068.30