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	$40.71	12.446%	$45.7768	$45.78	$45.80	$45.80
Purchase #2	$178.73	3.545%	$185.066	$185.07	$185.05	$185.10
Purchase #3	$89.68	11.302%	$99.8156	$99.82	$99.80	$99.80
Purchase #4	$193.99	12.637%	$218.5045	$218.50	$218.50	$218.50
Purchase #5	$118.45	4.146%	$123.3609	$123.36	$123.35	$123.40
Purchase #6	$240.29	5.480%	$253.4579	$253.46	$253.45	$253.50
Purchase #7	$134.33	11.525%	$149.8115	$149.81	$149.80	$149.80
7 purchase totals =	$996.18		$1,075.7932	$1,075.80	$1,075.75	$1,075.90