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	$158.83	9.158%	$173.3757	$173.38	$173.40	$173.40
Purchase #2	$150.59	11.644%	$168.1247	$168.12	$168.10	$168.10
Purchase #3	$229.51	5.667%	$242.5163	$242.52	$242.50	$242.50
Purchase #4	$33.74	5.159%	$35.4806	$35.48	$35.50	$35.50
Purchase #5	$162.73	4.411%	$169.908	$169.91	$169.90	$169.90
Purchase #6	$248.26	4.312%	$258.965	$258.97	$258.95	$259.00
Purchase #7	$44.35	4.618%	$46.3981	$46.40	$46.40	$46.40
7 purchase totals =	$1,028.01		$1,094.7684	$1,094.78	$1,094.75	$1,094.80