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	$31.87	10.308%	$35.1552	$35.16	$35.15	$35.20
Purchase #2	$57.84	4.250%	$60.2982	$60.30	$60.30	$60.30
Purchase #3	$90.32	8.614%	$98.1002	$98.10	$98.10	$98.10
Purchase #4	$47.47	12.311%	$53.314	$53.31	$53.30	$53.30
Purchase #5	$31.32	3.676%	$32.4713	$32.47	$32.45	$32.50
Purchase #6	$249.40	8.333%	$270.1825	$270.18	$270.20	$270.20
Purchase #7	$193.31	10.592%	$213.7854	$213.79	$213.80	$213.80
7 purchase totals =	$701.53		$763.3068	$763.31	$763.30	$763.40