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	$196.56	6.666%	$209.6627	$209.66	$209.65	$209.70
Purchase #2	$191.27	4.342%	$199.5749	$199.57	$199.55	$199.60
Purchase #3	$215.76	13.789%	$245.5111	$245.51	$245.50	$245.50
Purchase #4	$106.31	6.806%	$113.5455	$113.55	$113.55	$113.50
Purchase #5	$76.86	4.715%	$80.4839	$80.48	$80.50	$80.50
Purchase #6	$64.73	3.355%	$66.9017	$66.90	$66.90	$66.90
Purchase #7	$27.62	3.622%	$28.6204	$28.62	$28.60	$28.60
7 purchase totals =	$879.11		$944.3002	$944.29	$944.25	$944.30