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	$31.86	12.283%	$35.7734	$35.77	$35.75	$35.80
Purchase #2	$174.90	5.388%	$184.3236	$184.32	$184.30	$184.30
Purchase #3	$184.93	3.845%	$192.0406	$192.04	$192.05	$192.00
Purchase #4	$234.78	3.414%	$242.7954	$242.80	$242.80	$242.80
Purchase #5	$232.48	4.752%	$243.5274	$243.53	$243.55	$243.50
Purchase #6	$208.80	11.689%	$233.2066	$233.21	$233.20	$233.20
Purchase #7	$86.88	4.181%	$90.5125	$90.51	$90.50	$90.50
7 purchase totals =	$1,154.63		$1,222.1795	$1,222.18	$1,222.15	$1,222.10