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	$104.93	9.124%	$114.5038	$114.50	$114.50	$114.50
Purchase #2	$133.67	9.294%	$146.0933	$146.09	$146.10	$146.10
Purchase #3	$148.63	10.771%	$164.6389	$164.64	$164.65	$164.60
Purchase #4	$149.33	6.868%	$159.586	$159.59	$159.60	$159.60
Purchase #5	$60.53	7.655%	$65.1636	$65.16	$65.15	$65.20
Purchase #6	$84.89	9.121%	$92.6328	$92.63	$92.65	$92.60
Purchase #7	$116.72	10.430%	$128.8939	$128.89	$128.90	$128.90
7 purchase totals =	$798.70		$871.5123	$871.50	$871.55	$871.50