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	$52.77	10.818%	$58.4787	$58.48	$58.50	$58.50
Purchase #2	$13.99	6.171%	$14.8533	$14.85	$14.85	$14.90
Purchase #3	$27.59	4.222%	$28.7548	$28.75	$28.75	$28.80
Purchase #4	$126.28	10.452%	$139.4788	$139.48	$139.50	$139.50
Purchase #5	$43.98	4.159%	$45.8091	$45.81	$45.80	$45.80
Purchase #6	$61.59	12.152%	$69.0744	$69.07	$69.05	$69.10
Purchase #7	$106.61	4.156%	$111.0407	$111.04	$111.05	$111.00
7 purchase totals =	$432.81		$467.4898	$467.48	$467.50	$467.60