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	$102.76	9.357%	$112.3753	$112.38	$112.40	$112.40
Purchase #2	$175.34	9.371%	$191.7711	$191.77	$191.75	$191.80
Purchase #3	$69.29	13.687%	$78.7737	$78.77	$78.75	$78.80
Purchase #4	$124.27	6.158%	$131.9225	$131.92	$131.90	$131.90
Purchase #5	$32.74	10.257%	$36.0981	$36.10	$36.10	$36.10
Purchase #6	$75.67	4.142%	$78.8043	$78.80	$78.80	$78.80
Purchase #7	$78.62	7.691%	$84.6667	$84.67	$84.65	$84.70
7 purchase totals =	$658.69		$714.4117	$714.41	$714.35	$714.50