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	$234.26	3.207%	$241.7727	$241.77	$241.75	$241.80
Purchase #2	$94.98	5.598%	$100.297	$100.30	$100.30	$100.30
Purchase #3	$142.57	6.105%	$151.2739	$151.27	$151.25	$151.30
Purchase #4	$190.98	12.744%	$215.3185	$215.32	$215.30	$215.30
Purchase #5	$139.82	5.870%	$148.0274	$148.03	$148.05	$148.00
Purchase #6	$67.90	13.848%	$77.3028	$77.30	$77.30	$77.30
Purchase #7	$65.45	9.169%	$71.4511	$71.45	$71.45	$71.50
7 purchase totals =	$935.96		$1,005.4434	$1,005.44	$1,005.40	$1,005.50