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	$144.59	11.258%	$160.8679	$160.87	$160.85	$160.90
Purchase #2	$167.79	13.272%	$190.0591	$190.06	$190.05	$190.10
Purchase #3	$148.31	5.102%	$155.8768	$155.88	$155.90	$155.90
Purchase #4	$194.85	11.704%	$217.6552	$217.66	$217.65	$217.70
Purchase #5	$10.88	4.519%	$11.3717	$11.37	$11.35	$11.40
Purchase #6	$161.39	4.411%	$168.5089	$168.51	$168.50	$168.50
Purchase #7	$218.53	3.349%	$225.8486	$225.85	$225.85	$225.80
7 purchase totals =	$1,046.34		$1,130.1882	$1,130.20	$1,130.15	$1,130.30