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	$129.56	9.158%	$141.4251	$141.43	$141.45	$141.40
Purchase #2	$66.74	6.395%	$71.008	$71.01	$71.00	$71.00
Purchase #3	$80.41	5.777%	$85.0553	$85.06	$85.05	$85.10
Purchase #4	$219.51	10.131%	$241.7486	$241.75	$241.75	$241.70
Purchase #5	$91.29	4.357%	$95.2675	$95.27	$95.25	$95.30
Purchase #6	$66.34	10.463%	$73.2812	$73.28	$73.30	$73.30
Purchase #7	$157.75	6.763%	$168.4186	$168.42	$168.40	$168.40
7 purchase totals =	$811.60		$876.2043	$876.22	$876.20	$876.20