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	$65.53	12.222%	$73.5391	$73.54	$73.55	$73.50
Purchase #2	$248.48	9.515%	$272.1229	$272.12	$272.10	$272.10
Purchase #3	$69.58	12.680%	$78.4027	$78.40	$78.40	$78.40
Purchase #4	$120.49	11.839%	$134.7548	$134.75	$134.75	$134.80
Purchase #5	$54.34	13.826%	$61.853	$61.85	$61.85	$61.90
Purchase #6	$186.29	6.426%	$198.261	$198.26	$198.25	$198.30
Purchase #7	$135.35	4.847%	$141.9104	$141.91	$141.90	$141.90
7 purchase totals =	$880.06		$960.8439	$960.83	$960.80	$960.90