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	$73.52	4.330%	$76.7034	$76.70	$76.70	$76.70
Purchase #2	$173.52	10.537%	$191.8038	$191.80	$191.80	$191.80
Purchase #3	$104.71	7.618%	$112.6868	$112.69	$112.70	$112.70
Purchase #4	$216.64	10.732%	$239.8898	$239.89	$239.90	$239.90
Purchase #5	$169.25	6.503%	$180.2563	$180.26	$180.25	$180.30
Purchase #6	$250.94	9.799%	$275.5296	$275.53	$275.55	$275.50
Purchase #7	$47.74	6.187%	$50.6937	$50.69	$50.70	$50.70
7 purchase totals =	$1,036.32		$1,127.5634	$1,127.56	$1,127.60	$1,127.60