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	$32.29	6.599%	$34.4208	$34.42	$34.40	$34.40
Purchase #2	$125.41	3.785%	$130.1568	$130.16	$130.15	$130.20
Purchase #3	$29.57	12.705%	$33.3269	$33.33	$33.35	$33.30
Purchase #4	$236.95	12.846%	$267.3886	$267.39	$267.40	$267.40
Purchase #5	$141.32	7.169%	$151.4512	$151.45	$151.45	$151.50
Purchase #6	$74.59	5.297%	$78.541	$78.54	$78.55	$78.50
Purchase #7	$214.79	3.809%	$222.9714	$222.97	$222.95	$223.00
7 purchase totals =	$854.92		$918.2567	$918.26	$918.25	$918.30