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	$128.67	9.231%	$140.5475	$140.55	$140.55	$140.50
Purchase #2	$180.94	7.293%	$194.136	$194.14	$194.15	$194.10
Purchase #3	$127.65	5.660%	$134.875	$134.88	$134.90	$134.90
Purchase #4	$168.30	12.367%	$189.1137	$189.11	$189.10	$189.10
Purchase #5	$21.47	11.792%	$24.0017	$24.00	$24.00	$24.00
Purchase #6	$33.60	12.753%	$37.885	$37.89	$37.90	$37.90
Purchase #7	$173.96	5.203%	$183.0111	$183.01	$183.00	$183.00
7 purchase totals =	$834.59		$903.5700	$903.58	$903.60	$903.50