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	$22.41	5.489%	$23.6401	$23.64	$23.65	$23.60
Purchase #2	$100.58	5.696%	$106.309	$106.31	$106.30	$106.30
Purchase #3	$214.85	5.456%	$226.5722	$226.57	$226.55	$226.60
Purchase #4	$157.70	4.369%	$164.5899	$164.59	$164.60	$164.60
Purchase #5	$46.90	7.714%	$50.5179	$50.52	$50.50	$50.50
Purchase #6	$28.63	12.173%	$32.1151	$32.12	$32.10	$32.10
Purchase #7	$123.89	3.173%	$127.821	$127.82	$127.80	$127.80
7 purchase totals =	$694.96		$731.5652	$731.57	$731.50	$731.50