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	$55.69	11.547%	$62.1205	$62.12	$62.10	$62.10
Purchase #2	$147.62	11.401%	$164.4502	$164.45	$164.45	$164.50
Purchase #3	$233.40	3.310%	$241.1255	$241.13	$241.15	$241.10
Purchase #4	$32.94	8.840%	$35.8519	$35.85	$35.85	$35.90
Purchase #5	$128.37	9.857%	$141.0234	$141.02	$141.00	$141.00
Purchase #6	$6.65	6.868%	$7.1067	$7.11	$7.10	$7.10
Purchase #7	$123.64	12.507%	$139.1037	$139.10	$139.10	$139.10
7 purchase totals =	$728.31		$790.7819	$790.78	$790.75	$790.80