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	$67.78	5.799%	$71.7106	$71.71	$71.70	$71.70
Purchase #2	$54.94	13.649%	$62.4388	$62.44	$62.45	$62.40
Purchase #3	$145.54	7.143%	$155.9359	$155.94	$155.95	$155.90
Purchase #4	$187.32	11.236%	$208.3673	$208.37	$208.35	$208.40
Purchase #5	$91.68	9.401%	$100.2988	$100.30	$100.30	$100.30
Purchase #6	$77.47	10.376%	$85.5083	$85.51	$85.50	$85.50
Purchase #7	$62.95	10.658%	$69.6592	$69.66	$69.65	$69.70
7 purchase totals =	$687.68		$753.9189	$753.93	$753.90	$753.90