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	$47.87	11.845%	$53.5402	$53.54	$53.55	$53.50
Purchase #2	$172.33	5.322%	$181.5014	$181.50	$181.50	$181.50
Purchase #3	$191.51	9.854%	$210.3814	$210.38	$210.40	$210.40
Purchase #4	$157.40	6.389%	$167.4563	$167.46	$167.45	$167.50
Purchase #5	$146.80	3.480%	$151.9086	$151.91	$151.90	$151.90
Purchase #6	$13.44	4.139%	$13.9963	$14.00	$14.00	$14.00
Purchase #7	$42.92	11.677%	$47.9318	$47.93	$47.95	$47.90
7 purchase totals =	$772.27		$826.7160	$826.72	$826.75	$826.70