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	$150.94	12.327%	$169.5464	$169.55	$169.55	$169.50
Purchase #2	$148.92	13.286%	$168.7055	$168.71	$168.70	$168.70
Purchase #3	$46.86	3.801%	$48.6411	$48.64	$48.65	$48.60
Purchase #4	$71.37	9.859%	$78.4064	$78.41	$78.40	$78.40
Purchase #5	$68.54	4.441%	$71.5839	$71.58	$71.60	$71.60
Purchase #6	$46.51	10.729%	$51.5001	$51.50	$51.50	$51.50
Purchase #7	$159.74	12.205%	$179.2363	$179.24	$179.25	$179.20
7 purchase totals =	$692.88		$767.6197	$767.63	$767.65	$767.50