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	$178.44	3.419%	$184.5409	$184.54	$184.55	$184.50
Purchase #2	$109.81	12.616%	$123.6636	$123.66	$123.65	$123.70
Purchase #3	$169.78	6.405%	$180.6544	$180.65	$180.65	$180.70
Purchase #4	$227.34	10.295%	$250.7447	$250.74	$250.75	$250.70
Purchase #5	$180.62	10.736%	$200.0114	$200.01	$200.00	$200.00
Purchase #6	$97.31	3.863%	$101.0691	$101.07	$101.05	$101.10
Purchase #7	$52.33	9.111%	$57.0978	$57.10	$57.10	$57.10
7 purchase totals =	$1,015.63		$1,097.7819	$1,097.77	$1,097.75	$1,097.80