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	$193.90	12.137%	$217.4336	$217.43	$217.45	$217.40
Purchase #2	$184.73	11.422%	$205.8299	$205.83	$205.85	$205.80
Purchase #3	$124.78	6.679%	$133.1141	$133.11	$133.10	$133.10
Purchase #4	$238.47	10.533%	$263.588	$263.59	$263.60	$263.60
Purchase #5	$37.76	11.451%	$42.0839	$42.08	$42.10	$42.10
Purchase #6	$35.46	5.343%	$37.3546	$37.35	$37.35	$37.40
Purchase #7	$162.36	8.319%	$175.8667	$175.87	$175.85	$175.90
7 purchase totals =	$977.46		$1,075.2708	$1,075.26	$1,075.30	$1,075.30