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	$34.59	4.727%	$36.2251	$36.23	$36.25	$36.20
Purchase #2	$238.69	5.203%	$251.109	$251.11	$251.10	$251.10
Purchase #3	$111.73	10.508%	$123.4706	$123.47	$123.45	$123.50
Purchase #4	$93.35	5.658%	$98.6317	$98.63	$98.65	$98.60
Purchase #5	$64.53	4.806%	$67.6313	$67.63	$67.65	$67.60
Purchase #6	$182.56	12.684%	$205.7159	$205.72	$205.70	$205.70
Purchase #7	$233.55	5.281%	$245.8838	$245.88	$245.90	$245.90
7 purchase totals =	$959.00		$1,028.6674	$1,028.67	$1,028.70	$1,028.60