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	$213.77	13.710%	$243.0779	$243.08	$243.10	$243.10
Purchase #2	$102.48	7.276%	$109.9364	$109.94	$109.95	$109.90
Purchase #3	$139.73	10.426%	$154.2982	$154.30	$154.30	$154.30
Purchase #4	$114.92	10.510%	$126.9981	$127.00	$127.00	$127.00
Purchase #5	$143.36	4.346%	$149.5904	$149.59	$149.60	$149.60
Purchase #6	$142.28	5.580%	$150.2192	$150.22	$150.20	$150.20
Purchase #7	$128.49	10.152%	$141.5343	$141.53	$141.55	$141.50
7 purchase totals =	$985.03		$1,075.6545	$1,075.66	$1,075.70	$1,075.60