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	$16.95	9.801%	$18.6113	$18.61	$18.60	$18.60
Purchase #2	$56.41	11.794%	$63.063	$63.06	$63.05	$63.10
Purchase #3	$110.75	13.222%	$125.3934	$125.39	$125.40	$125.40
Purchase #4	$236.77	11.542%	$264.098	$264.10	$264.10	$264.10
Purchase #5	$32.89	9.794%	$36.1112	$36.11	$36.10	$36.10
Purchase #6	$96.59	4.178%	$100.6255	$100.63	$100.65	$100.60
Purchase #7	$248.76	5.559%	$262.5886	$262.59	$262.60	$262.60
7 purchase totals =	$799.12		$870.4910	$870.49	$870.50	$870.50