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	$67.41	7.757%	$72.639	$72.64	$72.65	$72.60
Purchase #2	$120.54	4.637%	$126.1294	$126.13	$126.15	$126.10
Purchase #3	$144.57	8.219%	$156.4522	$156.45	$156.45	$156.50
Purchase #4	$44.87	11.159%	$49.877	$49.88	$49.90	$49.90
Purchase #5	$73.35	7.576%	$78.907	$78.91	$78.90	$78.90
Purchase #6	$24.36	12.583%	$27.4252	$27.43	$27.45	$27.40
Purchase #7	$45.96	7.666%	$49.4833	$49.48	$49.50	$49.50
7 purchase totals =	$521.06		$560.9131	$560.92	$561.00	$560.90