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	$128.40	9.517%	$140.6198	$140.62	$140.60	$140.60
Purchase #2	$243.59	6.631%	$259.7425	$259.74	$259.75	$259.70
Purchase #3	$86.26	11.677%	$96.3326	$96.33	$96.35	$96.30
Purchase #4	$91.57	13.152%	$103.6133	$103.61	$103.60	$103.60
Purchase #5	$31.44	7.683%	$33.8555	$33.86	$33.85	$33.90
Purchase #6	$131.76	12.189%	$147.8202	$147.82	$147.80	$147.80
Purchase #7	$162.82	4.179%	$169.6242	$169.62	$169.60	$169.60
7 purchase totals =	$875.84		$951.6081	$951.60	$951.55	$951.50