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	$74.91	13.844%	$85.2805	$85.28	$85.30	$85.30
Purchase #2	$181.55	4.340%	$189.4293	$189.43	$189.45	$189.40
Purchase #3	$123.84	5.703%	$130.9026	$130.90	$130.90	$130.90
Purchase #4	$6.74	10.321%	$7.4356	$7.44	$7.45	$7.40
Purchase #5	$230.31	3.702%	$238.8361	$238.84	$238.85	$238.80
Purchase #6	$172.91	9.796%	$189.8483	$189.85	$189.85	$189.80
Purchase #7	$243.37	7.371%	$261.3088	$261.31	$261.30	$261.30
7 purchase totals =	$1,033.63		$1,103.0412	$1,103.05	$1,103.10	$1,102.90