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	$13.59	5.423%	$14.327	$14.33	$14.35	$14.30
Purchase #2	$99.64	12.589%	$112.1837	$112.18	$112.20	$112.20
Purchase #3	$173.56	7.833%	$187.155	$187.16	$187.15	$187.20
Purchase #4	$13.31	8.604%	$14.4552	$14.46	$14.45	$14.50
Purchase #5	$155.56	12.286%	$174.6721	$174.67	$174.65	$174.70
Purchase #6	$201.92	6.206%	$214.4512	$214.45	$214.45	$214.50
Purchase #7	$83.67	8.250%	$90.5728	$90.57	$90.55	$90.60
7 purchase totals =	$741.25		$807.8170	$807.82	$807.80	$808.00