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	$85.86	12.160%	$96.3006	$96.30	$96.30	$96.30
Purchase #2	$72.77	7.165%	$77.984	$77.98	$78.00	$78.00
Purchase #3	$38.89	10.301%	$42.8961	$42.90	$42.90	$42.90
Purchase #4	$78.77	8.155%	$85.1937	$85.19	$85.20	$85.20
Purchase #5	$234.51	3.185%	$241.9791	$241.98	$242.00	$242.00
Purchase #6	$6.38	8.489%	$6.9216	$6.92	$6.90	$6.90
Purchase #7	$140.85	4.713%	$147.4883	$147.49	$147.50	$147.50
7 purchase totals =	$658.03		$698.7634	$698.76	$698.80	$698.80