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	$81.51	13.425%	$92.4527	$92.45	$92.45	$92.50
Purchase #2	$190.29	10.421%	$210.1201	$210.12	$210.10	$210.10
Purchase #3	$77.72	10.121%	$85.586	$85.59	$85.60	$85.60
Purchase #4	$225.92	5.400%	$238.1197	$238.12	$238.10	$238.10
Purchase #5	$20.53	3.189%	$21.1847	$21.18	$21.20	$21.20
Purchase #6	$89.44	13.745%	$101.7335	$101.73	$101.75	$101.70
Purchase #7	$199.98	9.211%	$218.4002	$218.40	$218.40	$218.40
7 purchase totals =	$885.39		$967.5969	$967.59	$967.60	$967.60