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	$95.45	8.345%	$103.4153	$103.42	$103.40	$103.40
Purchase #2	$233.96	4.789%	$245.1643	$245.16	$245.15	$245.20
Purchase #3	$202.51	9.364%	$221.473	$221.47	$221.45	$221.50
Purchase #4	$138.93	3.534%	$143.8398	$143.84	$143.85	$143.80
Purchase #5	$80.50	11.837%	$90.0288	$90.03	$90.05	$90.00
Purchase #6	$89.77	6.392%	$95.5081	$95.51	$95.50	$95.50
Purchase #7	$162.62	5.673%	$171.8454	$171.85	$171.85	$171.80
7 purchase totals =	$1,003.74		$1,071.2747	$1,071.28	$1,071.25	$1,071.20