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	$157.73	10.649%	$174.5267	$174.53	$174.55	$174.50
Purchase #2	$13.79	3.780%	$14.3113	$14.31	$14.30	$14.30
Purchase #3	$205.50	3.733%	$213.1713	$213.17	$213.15	$213.20
Purchase #4	$37.36	3.161%	$38.5409	$38.54	$38.55	$38.50
Purchase #5	$52.99	11.548%	$59.1093	$59.11	$59.10	$59.10
Purchase #6	$124.57	13.827%	$141.7943	$141.79	$141.80	$141.80
Purchase #7	$164.89	11.302%	$183.5259	$183.53	$183.55	$183.50
7 purchase totals =	$756.83		$824.9797	$824.98	$825.00	$824.90