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	$103.85	10.616%	$114.8747	$114.87	$114.85	$114.90
Purchase #2	$111.77	13.425%	$126.7751	$126.78	$126.80	$126.80
Purchase #3	$159.51	13.272%	$180.6802	$180.68	$180.70	$180.70
Purchase #4	$64.78	13.457%	$73.4974	$73.50	$73.50	$73.50
Purchase #5	$195.41	12.479%	$219.7952	$219.80	$219.80	$219.80
Purchase #6	$180.78	5.589%	$190.8838	$190.88	$190.90	$190.90
Purchase #7	$157.78	7.327%	$169.3405	$169.34	$169.35	$169.30
7 purchase totals =	$973.88		$1,075.8469	$1,075.85	$1,075.90	$1,075.90