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	$127.36	4.321%	$132.8632	$132.86	$132.85	$132.90
Purchase #2	$165.85	10.256%	$182.8596	$182.86	$182.85	$182.90
Purchase #3	$24.34	6.302%	$25.8739	$25.87	$25.85	$25.90
Purchase #4	$81.63	5.610%	$86.2094	$86.21	$86.20	$86.20
Purchase #5	$79.96	11.521%	$89.1722	$89.17	$89.15	$89.20
Purchase #6	$143.69	12.524%	$161.6857	$161.69	$161.70	$161.70
Purchase #7	$95.89	6.328%	$101.9579	$101.96	$101.95	$102.00
7 purchase totals =	$718.72		$780.6219	$780.62	$780.55	$780.80