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	$138.90	9.600%	$152.2344	$152.23	$152.25	$152.20
Purchase #2	$7.79	7.483%	$8.3729	$8.37	$8.35	$8.40
Purchase #3	$145.73	11.570%	$162.591	$162.59	$162.60	$162.60
Purchase #4	$203.41	13.841%	$231.564	$231.56	$231.55	$231.60
Purchase #5	$67.59	3.527%	$69.9739	$69.97	$69.95	$70.00
Purchase #6	$113.64	12.199%	$127.5029	$127.50	$127.50	$127.50
Purchase #7	$137.53	10.354%	$151.7699	$151.77	$151.75	$151.80
7 purchase totals =	$814.59		$904.0090	$903.99	$903.95	$904.10