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	$146.49	7.507%	$157.487	$157.49	$157.50	$157.50
Purchase #2	$77.41	6.651%	$82.5585	$82.56	$82.55	$82.60
Purchase #3	$108.81	8.423%	$117.9751	$117.98	$118.00	$118.00
Purchase #4	$103.92	11.870%	$116.2553	$116.26	$116.25	$116.30
Purchase #5	$114.88	9.262%	$125.5202	$125.52	$125.50	$125.50
Purchase #6	$113.89	8.276%	$123.3155	$123.32	$123.30	$123.30
Purchase #7	$44.65	3.799%	$46.3463	$46.35	$46.35	$46.30
7 purchase totals =	$710.05		$769.4579	$769.48	$769.45	$769.50