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	$144.55	7.112%	$154.8304	$154.83	$154.85	$154.80
Purchase #2	$18.83	7.275%	$20.1999	$20.20	$20.20	$20.20
Purchase #3	$113.88	8.427%	$123.4767	$123.48	$123.50	$123.50
Purchase #4	$93.39	11.110%	$103.7656	$103.77	$103.75	$103.80
Purchase #5	$72.25	8.541%	$78.4209	$78.42	$78.40	$78.40
Purchase #6	$61.31	8.274%	$66.3828	$66.38	$66.40	$66.40
Purchase #7	$229.80	9.457%	$251.5322	$251.53	$251.55	$251.50
7 purchase totals =	$734.01		$798.6085	$798.61	$798.65	$798.60