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	$103.78	7.679%	$111.7493	$111.75	$111.75	$111.70
Purchase #2	$143.51	6.303%	$152.5554	$152.56	$152.55	$152.60
Purchase #3	$215.73	4.390%	$225.2005	$225.20	$225.20	$225.20
Purchase #4	$101.35	4.383%	$105.7922	$105.79	$105.80	$105.80
Purchase #5	$215.28	11.377%	$239.7724	$239.77	$239.75	$239.80
Purchase #6	$156.81	4.601%	$164.0248	$164.02	$164.00	$164.00
Purchase #7	$119.69	9.672%	$131.2664	$131.27	$131.25	$131.30
7 purchase totals =	$1,056.15		$1,130.3610	$1,130.36	$1,130.30	$1,130.40