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	$203.73	11.717%	$227.601	$227.60	$227.60	$227.60
Purchase #2	$75.50	3.689%	$78.2852	$78.29	$78.30	$78.30
Purchase #3	$39.64	3.212%	$40.9132	$40.91	$40.90	$40.90
Purchase #4	$94.35	12.695%	$106.3277	$106.33	$106.35	$106.30
Purchase #5	$29.91	6.437%	$31.8353	$31.84	$31.85	$31.80
Purchase #6	$90.65	4.805%	$95.0057	$95.01	$95.00	$95.00
Purchase #7	$90.76	4.753%	$95.0738	$95.07	$95.05	$95.10
7 purchase totals =	$624.54		$675.0419	$675.05	$675.05	$675.00