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	$193.56	11.610%	$216.0323	$216.03	$216.05	$216.00
Purchase #2	$18.56	13.427%	$21.0521	$21.05	$21.05	$21.10
Purchase #3	$87.33	7.592%	$93.9601	$93.96	$93.95	$94.00
Purchase #4	$217.78	11.699%	$243.2581	$243.26	$243.25	$243.30
Purchase #5	$103.64	10.150%	$114.1595	$114.16	$114.15	$114.20
Purchase #6	$199.96	11.183%	$222.3215	$222.32	$222.30	$222.30
Purchase #7	$97.42	3.183%	$100.5209	$100.52	$100.50	$100.50
7 purchase totals =	$918.25		$1,011.3045	$1,011.30	$1,011.25	$1,011.40