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	$49.64	6.318%	$52.7763	$52.78	$52.80	$52.80
Purchase #2	$135.34	10.854%	$150.0298	$150.03	$150.05	$150.00
Purchase #3	$244.66	9.515%	$267.9394	$267.94	$267.95	$267.90
Purchase #4	$202.78	10.278%	$223.6217	$223.62	$223.60	$223.60
Purchase #5	$32.90	7.238%	$35.2813	$35.28	$35.30	$35.30
Purchase #6	$250.25	6.390%	$266.241	$266.24	$266.25	$266.20
Purchase #7	$161.60	3.272%	$166.8876	$166.89	$166.90	$166.90
7 purchase totals =	$1,077.17		$1,162.7771	$1,162.78	$1,162.85	$1,162.70