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	$19.49	5.658%	$20.5927	$20.59	$20.60	$20.60
Purchase #2	$85.44	4.406%	$89.2045	$89.20	$89.20	$89.20
Purchase #3	$33.78	6.420%	$35.9487	$35.95	$35.95	$35.90
Purchase #4	$236.35	9.541%	$258.9002	$258.90	$258.90	$258.90
Purchase #5	$150.48	8.496%	$163.2648	$163.26	$163.25	$163.30
Purchase #6	$192.43	9.382%	$210.4838	$210.48	$210.50	$210.50
Purchase #7	$222.52	7.560%	$239.3425	$239.34	$239.35	$239.30
7 purchase totals =	$940.49		$1,017.7372	$1,017.72	$1,017.75	$1,017.70