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	$157.65	6.606%	$168.0644	$168.06	$168.05	$168.10
Purchase #2	$33.43	13.541%	$37.9568	$37.96	$37.95	$38.00
Purchase #3	$79.28	11.758%	$88.6017	$88.60	$88.60	$88.60
Purchase #4	$33.28	13.369%	$37.7292	$37.73	$37.75	$37.70
Purchase #5	$158.85	8.349%	$172.1124	$172.11	$172.10	$172.10
Purchase #6	$210.79	10.201%	$232.2927	$232.29	$232.30	$232.30
Purchase #7	$105.59	10.258%	$116.4214	$116.42	$116.40	$116.40
7 purchase totals =	$778.87		$853.1786	$853.17	$853.15	$853.20