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	$152.51	10.176%	$168.0294	$168.03	$168.05	$168.00
Purchase #2	$25.39	10.693%	$28.105	$28.11	$28.10	$28.10
Purchase #3	$116.57	11.112%	$129.5233	$129.52	$129.50	$129.50
Purchase #4	$172.70	10.521%	$190.8698	$190.87	$190.85	$190.90
Purchase #5	$49.62	3.678%	$51.445	$51.45	$51.45	$51.40
Purchase #6	$105.67	11.556%	$117.8812	$117.88	$117.90	$117.90
Purchase #7	$25.40	10.437%	$28.051	$28.05	$28.05	$28.10
7 purchase totals =	$647.86		$713.9047	$713.91	$713.90	$713.90