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	$172.89	10.103%	$190.3571	$190.36	$190.35	$190.40
Purchase #2	$139.97	7.149%	$149.9765	$149.98	$150.00	$150.00
Purchase #3	$146.35	4.135%	$152.4016	$152.40	$152.40	$152.40
Purchase #4	$144.59	12.595%	$162.8011	$162.80	$162.80	$162.80
Purchase #5	$151.51	13.782%	$172.3911	$172.39	$172.40	$172.40
Purchase #6	$12.50	13.842%	$14.2303	$14.23	$14.25	$14.20
Purchase #7	$210.32	9.292%	$229.8629	$229.86	$229.85	$229.90
7 purchase totals =	$978.13		$1,072.0206	$1,072.02	$1,072.05	$1,072.10