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	$34.29	7.514%	$36.8666	$36.87	$36.85	$36.90
Purchase #2	$109.29	9.522%	$119.6966	$119.70	$119.70	$119.70
Purchase #3	$75.66	3.219%	$78.0955	$78.10	$78.10	$78.10
Purchase #4	$65.87	10.214%	$72.598	$72.60	$72.60	$72.60
Purchase #5	$198.45	6.770%	$211.8851	$211.89	$211.90	$211.90
Purchase #6	$56.68	5.570%	$59.8371	$59.84	$59.85	$59.80
Purchase #7	$147.32	3.678%	$152.7384	$152.74	$152.75	$152.70
7 purchase totals =	$687.56		$731.7173	$731.74	$731.75	$731.70