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	$204.46	11.377%	$227.7214	$227.72	$227.70	$227.70
Purchase #2	$59.84	12.528%	$67.3368	$67.34	$67.35	$67.30
Purchase #3	$81.86	8.641%	$88.9335	$88.93	$88.95	$88.90
Purchase #4	$149.71	8.758%	$162.8216	$162.82	$162.80	$162.80
Purchase #5	$123.34	10.760%	$136.6114	$136.61	$136.60	$136.60
Purchase #6	$187.94	12.776%	$211.9512	$211.95	$211.95	$212.00
Purchase #7	$162.77	5.787%	$172.1895	$172.19	$172.20	$172.20
7 purchase totals =	$969.92		$1,067.5654	$1,067.56	$1,067.55	$1,067.50