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	$204.26	13.524%	$231.8841	$231.88	$231.90	$231.90
Purchase #2	$90.57	6.649%	$96.592	$96.59	$96.60	$96.60
Purchase #3	$107.88	4.411%	$112.6386	$112.64	$112.65	$112.60
Purchase #4	$28.51	9.125%	$31.1115	$31.11	$31.10	$31.10
Purchase #5	$68.35	5.333%	$71.9951	$72.00	$72.00	$72.00
Purchase #6	$239.66	6.707%	$255.734	$255.73	$255.75	$255.70
Purchase #7	$213.30	13.154%	$241.3575	$241.36	$241.35	$241.40
7 purchase totals =	$952.53		$1,041.3128	$1,041.31	$1,041.35	$1,041.30