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	$78.53	8.825%	$85.4603	$85.46	$85.45	$85.50
Purchase #2	$164.78	11.159%	$183.1678	$183.17	$183.15	$183.20
Purchase #3	$160.94	11.675%	$179.7297	$179.73	$179.75	$179.70
Purchase #4	$115.82	9.353%	$126.6526	$126.65	$126.65	$126.70
Purchase #5	$45.37	6.644%	$48.3844	$48.38	$48.40	$48.40
Purchase #6	$208.90	4.389%	$218.0686	$218.07	$218.05	$218.10
Purchase #7	$89.54	7.500%	$96.2555	$96.26	$96.25	$96.30
7 purchase totals =	$863.88		$937.7189	$937.72	$937.70	$937.90