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	$152.26	3.787%	$158.0261	$158.03	$158.05	$158.00
Purchase #2	$205.74	13.665%	$233.8544	$233.85	$233.85	$233.90
Purchase #3	$99.27	10.361%	$109.5554	$109.56	$109.55	$109.60
Purchase #4	$219.59	4.306%	$229.0455	$229.05	$229.05	$229.00
Purchase #5	$32.68	4.805%	$34.2503	$34.25	$34.25	$34.30
Purchase #6	$95.56	6.626%	$101.8918	$101.89	$101.90	$101.90
Purchase #7	$213.62	6.306%	$227.0909	$227.09	$227.10	$227.10
7 purchase totals =	$1,018.72		$1,093.7144	$1,093.72	$1,093.75	$1,093.80