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	$145.98	3.553%	$151.1667	$151.17	$151.15	$151.20
Purchase #2	$165.65	9.116%	$180.7507	$180.75	$180.75	$180.80
Purchase #3	$128.48	11.183%	$142.8479	$142.85	$142.85	$142.80
Purchase #4	$211.47	3.505%	$218.882	$218.88	$218.90	$218.90
Purchase #5	$38.41	8.318%	$41.6049	$41.60	$41.60	$41.60
Purchase #6	$133.43	12.420%	$150.002	$150.00	$150.00	$150.00
Purchase #7	$95.93	8.165%	$103.7627	$103.76	$103.75	$103.80
7 purchase totals =	$919.35		$989.0169	$989.01	$989.00	$989.10