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	$235.30	13.297%	$266.5878	$266.59	$266.60	$266.60
Purchase #2	$72.28	11.197%	$80.3732	$80.37	$80.35	$80.40
Purchase #3	$241.44	9.207%	$263.6694	$263.67	$263.65	$263.70
Purchase #4	$161.40	6.549%	$171.9701	$171.97	$171.95	$172.00
Purchase #5	$151.94	11.312%	$169.1275	$169.13	$169.15	$169.10
Purchase #6	$147.54	5.650%	$155.876	$155.88	$155.90	$155.90
Purchase #7	$65.48	8.862%	$71.2828	$71.28	$71.30	$71.30
7 purchase totals =	$1,075.38		$1,178.8868	$1,178.89	$1,178.90	$1,179.00