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	$157.44	9.787%	$172.8487	$172.85	$172.85	$172.80
Purchase #2	$172.63	9.778%	$189.5098	$189.51	$189.50	$189.50
Purchase #3	$45.85	6.355%	$48.7638	$48.76	$48.75	$48.80
Purchase #4	$95.51	4.264%	$99.5825	$99.58	$99.60	$99.60
Purchase #5	$148.70	9.301%	$162.5306	$162.53	$162.55	$162.50
Purchase #6	$197.86	6.764%	$211.2433	$211.24	$211.25	$211.20
Purchase #7	$40.45	13.656%	$45.9739	$45.97	$45.95	$46.00
7 purchase totals =	$858.44		$930.4526	$930.44	$930.45	$930.40