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	$33.37	4.518%	$34.8777	$34.88	$34.90	$34.90
Purchase #2	$100.60	5.474%	$106.1068	$106.11	$106.10	$106.10
Purchase #3	$173.91	9.857%	$191.0523	$191.05	$191.05	$191.10
Purchase #4	$31.26	7.206%	$33.5126	$33.51	$33.50	$33.50
Purchase #5	$143.33	6.639%	$152.8457	$152.85	$152.85	$152.80
Purchase #6	$205.41	5.217%	$216.1262	$216.13	$216.15	$216.10
Purchase #7	$33.27	6.545%	$35.4475	$35.45	$35.45	$35.40
7 purchase totals =	$721.15		$769.9688	$769.98	$770.00	$769.90