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	$29.30	4.431%	$30.5983	$30.60	$30.60	$30.60
Purchase #2	$96.71	7.146%	$103.6209	$103.62	$103.60	$103.60
Purchase #3	$81.74	10.118%	$90.0105	$90.01	$90.00	$90.00
Purchase #4	$67.69	5.126%	$71.1598	$71.16	$71.15	$71.20
Purchase #5	$193.72	10.216%	$213.5104	$213.51	$213.50	$213.50
Purchase #6	$103.47	4.838%	$108.4759	$108.48	$108.50	$108.50
Purchase #7	$129.28	10.361%	$142.6747	$142.67	$142.65	$142.70
7 purchase totals =	$701.91		$760.0505	$760.05	$760.00	$760.10