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	$232.42	9.478%	$254.4488	$254.45	$254.45	$254.40
Purchase #2	$35.78	5.849%	$37.8728	$37.87	$37.85	$37.90
Purchase #3	$160.25	4.137%	$166.8795	$166.88	$166.90	$166.90
Purchase #4	$33.97	9.338%	$37.1421	$37.14	$37.15	$37.10
Purchase #5	$153.74	5.507%	$162.2065	$162.21	$162.20	$162.20
Purchase #6	$51.30	3.564%	$53.1283	$53.13	$53.15	$53.10
Purchase #7	$209.90	8.831%	$228.4363	$228.44	$228.45	$228.40
7 purchase totals =	$877.36		$940.1143	$940.12	$940.15	$940.00