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	$203.36	6.560%	$216.7004	$216.70	$216.70	$216.70
Purchase #2	$122.52	3.861%	$127.2505	$127.25	$127.25	$127.30
Purchase #3	$146.84	11.736%	$164.0731	$164.07	$164.05	$164.10
Purchase #4	$136.78	3.706%	$141.8491	$141.85	$141.85	$141.80
Purchase #5	$193.34	11.518%	$215.6089	$215.61	$215.60	$215.60
Purchase #6	$31.50	7.684%	$33.9205	$33.92	$33.90	$33.90
Purchase #7	$188.29	12.111%	$211.0938	$211.09	$211.10	$211.10
7 purchase totals =	$1,022.63		$1,110.4963	$1,110.49	$1,110.45	$1,110.50