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	$198.37	3.278%	$204.8726	$204.87	$204.85	$204.90
Purchase #2	$71.60	9.572%	$78.4536	$78.45	$78.45	$78.50
Purchase #3	$123.76	13.781%	$140.8154	$140.82	$140.80	$140.80
Purchase #4	$59.74	9.743%	$65.5605	$65.56	$65.55	$65.60
Purchase #5	$247.66	6.603%	$264.013	$264.01	$264.00	$264.00
Purchase #6	$191.90	8.659%	$208.5166	$208.52	$208.50	$208.50
Purchase #7	$249.89	4.352%	$260.7652	$260.77	$260.75	$260.80
7 purchase totals =	$1,142.92		$1,222.9969	$1,223.00	$1,222.90	$1,223.10