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	$12.79	3.565%	$13.246	$13.25	$13.25	$13.20
Purchase #2	$69.63	12.697%	$78.4709	$78.47	$78.45	$78.50
Purchase #3	$152.73	10.321%	$168.4933	$168.49	$168.50	$168.50
Purchase #4	$207.48	13.515%	$235.5209	$235.52	$235.50	$235.50
Purchase #5	$211.78	12.520%	$238.2949	$238.29	$238.30	$238.30
Purchase #6	$190.79	7.295%	$204.7081	$204.71	$204.70	$204.70
Purchase #7	$62.74	12.217%	$70.4049	$70.40	$70.40	$70.40
7 purchase totals =	$907.94		$1,009.1390	$1,009.13	$1,009.10	$1,009.10