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	$58.95	5.153%	$61.9877	$61.99	$62.00	$62.00
Purchase #2	$158.32	8.413%	$171.6395	$171.64	$171.65	$171.60
Purchase #3	$156.80	12.799%	$176.8688	$176.87	$176.85	$176.90
Purchase #4	$85.86	11.103%	$95.393	$95.39	$95.40	$95.40
Purchase #5	$52.85	3.293%	$54.5904	$54.59	$54.60	$54.60
Purchase #6	$91.95	8.656%	$99.9092	$99.91	$99.90	$99.90
Purchase #7	$247.50	5.219%	$260.417	$260.42	$260.40	$260.40
7 purchase totals =	$852.23		$920.8056	$920.81	$920.80	$920.80