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	$31.63	11.366%	$35.2251	$35.23	$35.25	$35.20
Purchase #2	$143.35	6.410%	$152.5387	$152.54	$152.55	$152.50
Purchase #3	$208.77	10.718%	$231.146	$231.15	$231.15	$231.10
Purchase #4	$244.89	3.760%	$254.0979	$254.10	$254.10	$254.10
Purchase #5	$203.78	9.657%	$223.459	$223.46	$223.45	$223.50
Purchase #6	$198.89	5.522%	$209.8727	$209.87	$209.85	$209.90
Purchase #7	$106.76	9.476%	$116.8766	$116.88	$116.90	$116.90
7 purchase totals =	$1,138.07		$1,223.2160	$1,223.23	$1,223.25	$1,223.20