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	$140.27	3.583%	$145.2959	$145.30	$145.30	$145.30
Purchase #2	$186.57	10.839%	$206.7923	$206.79	$206.80	$206.80
Purchase #3	$35.81	4.712%	$37.4974	$37.50	$37.50	$37.50
Purchase #4	$56.71	13.417%	$64.3188	$64.32	$64.30	$64.30
Purchase #5	$153.36	7.291%	$164.5415	$164.54	$164.55	$164.50
Purchase #6	$218.71	11.209%	$243.2252	$243.23	$243.25	$243.20
Purchase #7	$152.71	12.700%	$172.1042	$172.10	$172.10	$172.10
7 purchase totals =	$944.14		$1,033.7753	$1,033.78	$1,033.80	$1,033.70