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	$138.72	11.644%	$154.8726	$154.87	$154.85	$154.90
Purchase #2	$78.46	3.107%	$80.8978	$80.90	$80.90	$80.90
Purchase #3	$57.61	4.664%	$60.2969	$60.30	$60.30	$60.30
Purchase #4	$227.33	8.690%	$247.085	$247.09	$247.10	$247.10
Purchase #5	$247.72	3.161%	$255.5504	$255.55	$255.55	$255.60
Purchase #6	$94.80	7.401%	$101.8161	$101.82	$101.80	$101.80
Purchase #7	$102.28	11.253%	$113.7896	$113.79	$113.80	$113.80
7 purchase totals =	$946.92		$1,014.3084	$1,014.32	$1,014.30	$1,014.40