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	$83.93	9.545%	$91.9411	$91.94	$91.95	$91.90
Purchase #2	$243.90	12.468%	$274.3095	$274.31	$274.30	$274.30
Purchase #3	$145.48	10.399%	$160.6085	$160.61	$160.60	$160.60
Purchase #4	$40.61	5.404%	$42.8046	$42.80	$42.80	$42.80
Purchase #5	$112.50	5.865%	$119.0981	$119.10	$119.10	$119.10
Purchase #6	$26.81	11.232%	$29.8213	$29.82	$29.80	$29.80
Purchase #7	$96.29	10.547%	$106.4457	$106.45	$106.45	$106.40
7 purchase totals =	$749.52		$825.0288	$825.03	$825.00	$824.90