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	$200.62	10.764%	$222.2147	$222.21	$222.20	$222.20
Purchase #2	$169.53	4.482%	$177.1283	$177.13	$177.15	$177.10
Purchase #3	$154.75	11.151%	$172.0062	$172.01	$172.00	$172.00
Purchase #4	$206.77	6.284%	$219.7634	$219.76	$219.75	$219.80
Purchase #5	$119.67	6.247%	$127.1458	$127.15	$127.15	$127.10
Purchase #6	$48.91	13.616%	$55.5696	$55.57	$55.55	$55.60
Purchase #7	$125.96	4.106%	$131.1319	$131.13	$131.15	$131.10
7 purchase totals =	$1,026.21		$1,104.9599	$1,104.96	$1,104.95	$1,104.90