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	$42.77	10.368%	$47.2044	$47.20	$47.20	$47.20
Purchase #2	$36.27	11.743%	$40.5292	$40.53	$40.55	$40.50
Purchase #3	$39.53	7.399%	$42.4548	$42.45	$42.45	$42.50
Purchase #4	$85.93	6.210%	$91.2663	$91.27	$91.25	$91.30
Purchase #5	$94.43	12.150%	$105.9032	$105.90	$105.90	$105.90
Purchase #6	$47.81	11.802%	$53.4525	$53.45	$53.45	$53.50
Purchase #7	$76.99	10.458%	$85.0416	$85.04	$85.05	$85.00
7 purchase totals =	$423.73		$465.8520	$465.84	$465.85	$465.90