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	$148.26	9.639%	$162.5508	$162.55	$162.55	$162.60
Purchase #2	$78.80	5.507%	$83.1395	$83.14	$83.15	$83.10
Purchase #3	$181.71	9.571%	$199.1015	$199.10	$199.10	$199.10
Purchase #4	$11.81	6.751%	$12.6073	$12.61	$12.60	$12.60
Purchase #5	$207.30	7.607%	$223.0693	$223.07	$223.05	$223.10
Purchase #6	$139.39	10.420%	$153.9144	$153.91	$153.90	$153.90
Purchase #7	$137.46	9.541%	$150.5751	$150.58	$150.60	$150.60
7 purchase totals =	$904.73		$984.9579	$984.96	$984.95	$985.00