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	$42.67	11.145%	$47.4256	$47.43	$47.45	$47.40
Purchase #2	$78.44	3.683%	$81.3289	$81.33	$81.35	$81.30
Purchase #3	$79.26	13.597%	$90.037	$90.04	$90.05	$90.00
Purchase #4	$63.99	11.700%	$71.4768	$71.48	$71.50	$71.50
Purchase #5	$18.51	5.296%	$19.4903	$19.49	$19.50	$19.50
Purchase #6	$173.69	5.141%	$182.6194	$182.62	$182.60	$182.60
Purchase #7	$96.96	10.161%	$106.8121	$106.81	$106.80	$106.80
7 purchase totals =	$553.52		$599.1901	$599.20	$599.25	$599.10