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	$173.45	4.716%	$181.6299	$181.63	$181.65	$181.60
Purchase #2	$76.95	7.353%	$82.6081	$82.61	$82.60	$82.60
Purchase #3	$37.38	13.639%	$42.4783	$42.48	$42.50	$42.50
Purchase #4	$225.89	7.179%	$242.1066	$242.11	$242.10	$242.10
Purchase #5	$9.43	11.639%	$10.5276	$10.53	$10.55	$10.50
Purchase #6	$223.31	7.150%	$239.2767	$239.28	$239.30	$239.30
Purchase #7	$234.26	9.470%	$256.4444	$256.44	$256.45	$256.40
7 purchase totals =	$980.67		$1,055.0716	$1,055.08	$1,055.15	$1,055.00