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	$95.50	11.397%	$106.3841	$106.38	$106.40	$106.40
Purchase #2	$40.84	7.851%	$44.0463	$44.05	$44.05	$44.00
Purchase #3	$116.91	12.408%	$131.4162	$131.42	$131.40	$131.40
Purchase #4	$116.39	12.552%	$130.9993	$131.00	$131.00	$131.00
Purchase #5	$53.85	12.354%	$60.5026	$60.50	$60.50	$60.50
Purchase #6	$108.54	13.430%	$123.1169	$123.12	$123.10	$123.10
Purchase #7	$202.64	3.401%	$209.5318	$209.53	$209.55	$209.50
7 purchase totals =	$734.67		$805.9972	$806.00	$806.00	$805.90