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	$150.96	9.488%	$165.2831	$165.28	$165.30	$165.30
Purchase #2	$73.82	9.660%	$80.951	$80.95	$80.95	$81.00
Purchase #3	$200.38	7.129%	$214.6651	$214.67	$214.65	$214.70
Purchase #4	$237.87	10.543%	$262.9486	$262.95	$262.95	$262.90
Purchase #5	$206.60	7.864%	$222.847	$222.85	$222.85	$222.80
Purchase #6	$100.72	9.124%	$109.9097	$109.91	$109.90	$109.90
Purchase #7	$145.89	3.415%	$150.8721	$150.87	$150.85	$150.90
7 purchase totals =	$1,116.24		$1,207.4766	$1,207.48	$1,207.45	$1,207.50