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	$24.83	10.275%	$27.3813	$27.38	$27.40	$27.40
Purchase #2	$225.65	12.765%	$254.4542	$254.45	$254.45	$254.50
Purchase #3	$65.66	11.670%	$73.3225	$73.32	$73.30	$73.30
Purchase #4	$67.64	5.375%	$71.2757	$71.28	$71.30	$71.30
Purchase #5	$194.61	9.713%	$213.5125	$213.51	$213.50	$213.50
Purchase #6	$189.89	6.663%	$202.5424	$202.54	$202.55	$202.50
Purchase #7	$210.38	10.752%	$233.0001	$233.00	$233.00	$233.00
7 purchase totals =	$978.66		$1,075.4887	$1,075.48	$1,075.50	$1,075.50