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	$147.32	7.634%	$158.5664	$158.57	$158.55	$158.60
Purchase #2	$158.93	4.411%	$165.9404	$165.94	$165.95	$165.90
Purchase #3	$218.30	13.798%	$248.421	$248.42	$248.40	$248.40
Purchase #4	$206.66	5.350%	$217.7163	$217.72	$217.70	$217.70
Purchase #5	$178.43	3.831%	$185.2657	$185.27	$185.25	$185.30
Purchase #6	$135.61	6.622%	$144.5901	$144.59	$144.60	$144.60
Purchase #7	$38.81	4.771%	$40.6616	$40.66	$40.65	$40.70
7 purchase totals =	$1,084.06		$1,161.1615	$1,161.17	$1,161.10	$1,161.20