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	$238.26	4.695%	$249.4463	$249.45	$249.45	$249.40
Purchase #2	$189.94	11.374%	$211.5438	$211.54	$211.55	$211.50
Purchase #3	$225.46	12.521%	$253.6898	$253.69	$253.70	$253.70
Purchase #4	$62.31	8.235%	$67.4412	$67.44	$67.45	$67.40
Purchase #5	$249.45	12.325%	$280.1947	$280.19	$280.20	$280.20
Purchase #6	$214.38	11.154%	$238.2919	$238.29	$238.30	$238.30
Purchase #7	$146.50	7.127%	$156.9411	$156.94	$156.95	$156.90
7 purchase totals =	$1,326.30		$1,457.5488	$1,457.54	$1,457.60	$1,457.40