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	$133.78	12.825%	$150.9373	$150.94	$150.95	$150.90
Purchase #2	$240.71	7.350%	$258.4022	$258.40	$258.40	$258.40
Purchase #3	$48.85	10.863%	$54.1566	$54.16	$54.15	$54.20
Purchase #4	$167.34	3.192%	$172.6815	$172.68	$172.70	$172.70
Purchase #5	$32.38	9.626%	$35.4969	$35.50	$35.50	$35.50
Purchase #6	$152.50	10.750%	$168.8938	$168.89	$168.90	$168.90
Purchase #7	$207.74	11.300%	$231.2146	$231.21	$231.20	$231.20
7 purchase totals =	$983.30		$1,071.7829	$1,071.78	$1,071.80	$1,071.80