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	$148.62	10.547%	$164.295	$164.30	$164.30	$164.30
Purchase #2	$167.40	3.221%	$172.792	$172.79	$172.80	$172.80
Purchase #3	$234.89	3.388%	$242.8481	$242.85	$242.85	$242.80
Purchase #4	$107.64	9.755%	$118.1403	$118.14	$118.15	$118.10
Purchase #5	$186.90	12.431%	$210.1335	$210.13	$210.15	$210.10
Purchase #6	$107.57	10.462%	$118.824	$118.82	$118.80	$118.80
Purchase #7	$202.73	13.356%	$229.8066	$229.81	$229.80	$229.80
7 purchase totals =	$1,155.75		$1,256.8395	$1,256.84	$1,256.85	$1,256.70