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	$125.39	4.446%	$130.9648	$130.96	$130.95	$131.00
Purchase #2	$86.96	4.184%	$90.5984	$90.60	$90.60	$90.60
Purchase #3	$203.90	7.475%	$219.1415	$219.14	$219.15	$219.10
Purchase #4	$142.87	9.588%	$156.5684	$156.57	$156.55	$156.60
Purchase #5	$31.48	5.672%	$33.2655	$33.27	$33.25	$33.30
Purchase #6	$96.51	4.499%	$100.852	$100.85	$100.85	$100.90
Purchase #7	$57.50	11.475%	$64.0981	$64.10	$64.10	$64.10
7 purchase totals =	$744.61		$795.4887	$795.49	$795.45	$795.60