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	$223.39	9.865%	$245.4274	$245.43	$245.45	$245.40
Purchase #2	$82.55	12.389%	$92.7771	$92.78	$92.80	$92.80
Purchase #3	$117.32	7.484%	$126.1002	$126.10	$126.10	$126.10
Purchase #4	$213.62	11.769%	$238.7609	$238.76	$238.75	$238.80
Purchase #5	$7.65	3.582%	$7.924	$7.92	$7.90	$7.90
Purchase #6	$122.39	8.625%	$132.9461	$132.95	$132.95	$132.90
Purchase #7	$156.48	11.148%	$173.9244	$173.92	$173.90	$173.90
7 purchase totals =	$923.40		$1,017.8601	$1,017.86	$1,017.85	$1,017.80