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	$144.88	9.367%	$158.4509	$158.45	$158.45	$158.50
Purchase #2	$169.30	9.144%	$184.7808	$184.78	$184.80	$184.80
Purchase #3	$178.94	7.113%	$191.668	$191.67	$191.65	$191.70
Purchase #4	$32.29	10.362%	$35.6359	$35.64	$35.65	$35.60
Purchase #5	$138.43	10.535%	$153.0136	$153.01	$153.00	$153.00
Purchase #6	$136.60	5.457%	$144.0543	$144.05	$144.05	$144.10
Purchase #7	$201.34	10.402%	$222.2834	$222.28	$222.30	$222.30
7 purchase totals =	$1,001.78		$1,089.8869	$1,089.88	$1,089.90	$1,090.00