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	$150.43	7.859%	$162.2523	$162.25	$162.25	$162.30
Purchase #2	$21.67	6.165%	$23.006	$23.01	$23.00	$23.00
Purchase #3	$243.65	9.303%	$266.3168	$266.32	$266.30	$266.30
Purchase #4	$67.34	6.750%	$71.8855	$71.89	$71.90	$71.90
Purchase #5	$213.72	5.430%	$225.325	$225.33	$225.35	$225.30
Purchase #6	$13.81	3.185%	$14.2498	$14.25	$14.25	$14.20
Purchase #7	$90.82	9.328%	$99.2917	$99.29	$99.30	$99.30
7 purchase totals =	$801.44		$862.3271	$862.34	$862.35	$862.30