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	$127.93	9.611%	$140.2254	$140.23	$140.25	$140.20
Purchase #2	$164.38	5.188%	$172.908	$172.91	$172.90	$172.90
Purchase #3	$83.88	9.171%	$91.5726	$91.57	$91.55	$91.60
Purchase #4	$169.39	9.287%	$185.1212	$185.12	$185.10	$185.10
Purchase #5	$197.76	10.104%	$217.7417	$217.74	$217.75	$217.70
Purchase #6	$66.80	6.555%	$71.1787	$71.18	$71.20	$71.20
Purchase #7	$209.38	12.728%	$236.0299	$236.03	$236.05	$236.00
7 purchase totals =	$1,019.52		$1,114.7775	$1,114.78	$1,114.80	$1,114.70