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	$126.46	4.572%	$132.2418	$132.24	$132.25	$132.20
Purchase #2	$59.88	3.393%	$61.9117	$61.91	$61.90	$61.90
Purchase #3	$214.66	10.545%	$237.2959	$237.30	$237.30	$237.30
Purchase #4	$219.85	10.214%	$242.3055	$242.31	$242.30	$242.30
Purchase #5	$43.43	4.271%	$45.2849	$45.28	$45.30	$45.30
Purchase #6	$242.45	13.614%	$275.4571	$275.46	$275.45	$275.50
Purchase #7	$112.91	13.348%	$127.9812	$127.98	$128.00	$128.00
7 purchase totals =	$1,019.64		$1,122.4781	$1,122.48	$1,122.50	$1,122.50