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	$231.55	10.334%	$255.4784	$255.48	$255.50	$255.50
Purchase #2	$33.27	6.665%	$35.4874	$35.49	$35.50	$35.50
Purchase #3	$220.38	3.573%	$228.2542	$228.25	$228.25	$228.30
Purchase #4	$209.75	8.356%	$227.2767	$227.28	$227.30	$227.30
Purchase #5	$153.32	5.862%	$162.3076	$162.31	$162.30	$162.30
Purchase #6	$36.52	7.433%	$39.2345	$39.23	$39.25	$39.20
Purchase #7	$155.63	3.215%	$160.6335	$160.63	$160.65	$160.60
7 purchase totals =	$1,040.42		$1,108.6723	$1,108.67	$1,108.75	$1,108.70