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	$55.76	10.578%	$61.6583	$61.66	$61.65	$61.70
Purchase #2	$104.31	5.254%	$109.7904	$109.79	$109.80	$109.80
Purchase #3	$53.69	12.313%	$60.3008	$60.30	$60.30	$60.30
Purchase #4	$60.72	11.743%	$67.8503	$67.85	$67.85	$67.90
Purchase #5	$145.45	7.612%	$156.5217	$156.52	$156.50	$156.50
Purchase #6	$166.29	12.873%	$187.6965	$187.70	$187.70	$187.70
Purchase #7	$147.63	10.817%	$163.5991	$163.60	$163.60	$163.60
7 purchase totals =	$733.85		$807.4171	$807.42	$807.40	$807.50