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	$150.30	11.197%	$167.1291	$167.13	$167.15	$167.10
Purchase #2	$166.50	10.817%	$184.5103	$184.51	$184.50	$184.50
Purchase #3	$103.95	7.691%	$111.9448	$111.94	$111.95	$111.90
Purchase #4	$121.25	5.240%	$127.6035	$127.60	$127.60	$127.60
Purchase #5	$31.74	11.147%	$35.2781	$35.28	$35.30	$35.30
Purchase #6	$7.89	6.557%	$8.4073	$8.41	$8.40	$8.40
Purchase #7	$204.85	4.130%	$213.3103	$213.31	$213.30	$213.30
7 purchase totals =	$786.48		$848.1834	$848.18	$848.20	$848.10