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	$53.64	10.792%	$59.4288	$59.43	$59.45	$59.40
Purchase #2	$32.41	9.644%	$35.5356	$35.54	$35.55	$35.50
Purchase #3	$6.82	9.244%	$7.4504	$7.45	$7.45	$7.50
Purchase #4	$184.53	7.813%	$198.9473	$198.95	$198.95	$198.90
Purchase #5	$152.92	8.125%	$165.3448	$165.34	$165.35	$165.30
Purchase #6	$46.47	11.796%	$51.9516	$51.95	$51.95	$52.00
Purchase #7	$36.76	10.284%	$40.5404	$40.54	$40.55	$40.50
7 purchase totals =	$513.55		$559.1989	$559.20	$559.25	$559.10