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	$74.98	10.675%	$82.9841	$82.98	$83.00	$83.00
Purchase #2	$154.81	8.828%	$168.4766	$168.48	$168.50	$168.50
Purchase #3	$84.58	3.140%	$87.2358	$87.24	$87.25	$87.20
Purchase #4	$19.77	9.205%	$21.5898	$21.59	$21.60	$21.60
Purchase #5	$60.70	4.148%	$63.2178	$63.22	$63.20	$63.20
Purchase #6	$72.63	7.621%	$78.1651	$78.17	$78.15	$78.20
Purchase #7	$215.25	4.476%	$224.8846	$224.88	$224.90	$224.90
7 purchase totals =	$682.72		$726.5538	$726.56	$726.60	$726.60