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	$151.42	11.772%	$169.2452	$169.25	$169.25	$169.20
Purchase #2	$35.85	5.598%	$37.8569	$37.86	$37.85	$37.90
Purchase #3	$117.72	12.491%	$132.4244	$132.42	$132.40	$132.40
Purchase #4	$142.34	5.666%	$150.405	$150.41	$150.40	$150.40
Purchase #5	$10.63	5.735%	$11.2396	$11.24	$11.25	$11.20
Purchase #6	$11.75	11.556%	$13.1078	$13.11	$13.10	$13.10
Purchase #7	$161.90	3.498%	$167.5633	$167.56	$167.55	$167.60
7 purchase totals =	$631.61		$681.8422	$681.85	$681.80	$681.80