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	$55.32	8.329%	$59.9276	$59.93	$59.95	$59.90
Purchase #2	$84.52	13.327%	$95.784	$95.78	$95.80	$95.80
Purchase #3	$232.57	13.766%	$264.5856	$264.59	$264.60	$264.60
Purchase #4	$90.49	7.592%	$97.36	$97.36	$97.35	$97.40
Purchase #5	$61.64	10.420%	$68.0629	$68.06	$68.05	$68.10
Purchase #6	$136.31	11.395%	$151.8425	$151.84	$151.85	$151.80
Purchase #7	$228.59	3.643%	$236.9175	$236.92	$236.90	$236.90
7 purchase totals =	$889.44		$974.4801	$974.48	$974.50	$974.50