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	$231.43	3.153%	$238.727	$238.73	$238.75	$238.70
Purchase #2	$236.51	7.613%	$254.5155	$254.52	$254.50	$254.50
Purchase #3	$232.28	10.311%	$256.2304	$256.23	$256.25	$256.20
Purchase #4	$219.97	11.499%	$245.2644	$245.26	$245.25	$245.30
Purchase #5	$163.81	6.745%	$174.859	$174.86	$174.85	$174.90
Purchase #6	$16.63	11.783%	$18.5895	$18.59	$18.60	$18.60
Purchase #7	$179.54	11.584%	$200.3379	$200.34	$200.35	$200.30
7 purchase totals =	$1,280.17		$1,388.5237	$1,388.53	$1,388.55	$1,388.50