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	$200.50	4.798%	$210.12	$210.12	$210.10	$210.10
Purchase #2	$188.80	10.383%	$208.4031	$208.40	$208.40	$208.40
Purchase #3	$55.99	9.571%	$61.3488	$61.35	$61.35	$61.30
Purchase #4	$127.45	3.137%	$131.4481	$131.45	$131.45	$131.40
Purchase #5	$141.99	13.645%	$161.3645	$161.36	$161.35	$161.40
Purchase #6	$152.55	9.661%	$167.2879	$167.29	$167.30	$167.30
Purchase #7	$244.46	6.560%	$260.4966	$260.50	$260.50	$260.50
7 purchase totals =	$1,111.74		$1,200.4690	$1,200.47	$1,200.45	$1,200.40