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	$131.58	10.713%	$145.6762	$145.68	$145.70	$145.70
Purchase #2	$215.35	8.740%	$234.1716	$234.17	$234.15	$234.20
Purchase #3	$114.94	10.640%	$127.1696	$127.17	$127.15	$127.20
Purchase #4	$45.80	7.692%	$49.3229	$49.32	$49.30	$49.30
Purchase #5	$152.28	4.136%	$158.5783	$158.58	$158.60	$158.60
Purchase #6	$160.87	11.641%	$179.5969	$179.60	$179.60	$179.60
Purchase #7	$32.36	10.678%	$35.8154	$35.82	$35.80	$35.80
7 purchase totals =	$853.18		$930.3309	$930.34	$930.30	$930.40