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	$33.79	13.837%	$38.4655	$38.47	$38.45	$38.50
Purchase #2	$159.69	7.393%	$171.4959	$171.50	$171.50	$171.50
Purchase #3	$168.67	10.648%	$186.63	$186.63	$186.65	$186.60
Purchase #4	$18.84	3.145%	$19.4325	$19.43	$19.45	$19.40
Purchase #5	$60.89	10.794%	$67.4625	$67.46	$67.45	$67.50
Purchase #6	$22.31	9.200%	$24.3625	$24.36	$24.35	$24.40
Purchase #7	$46.66	11.767%	$52.1505	$52.15	$52.15	$52.20
7 purchase totals =	$510.85		$559.9994	$560.00	$560.00	$560.10