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	$67.73	8.359%	$73.3916	$73.39	$73.40	$73.40
Purchase #2	$111.49	6.569%	$118.8138	$118.81	$118.80	$118.80
Purchase #3	$137.31	3.814%	$142.547	$142.55	$142.55	$142.50
Purchase #4	$114.25	8.225%	$123.6471	$123.65	$123.65	$123.60
Purchase #5	$45.64	10.487%	$50.4263	$50.43	$50.45	$50.40
Purchase #6	$90.79	3.688%	$94.1383	$94.14	$94.15	$94.10
Purchase #7	$250.83	9.460%	$274.5585	$274.56	$274.55	$274.60
7 purchase totals =	$818.04		$877.5226	$877.53	$877.55	$877.40