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	$103.83	4.432%	$108.4317	$108.43	$108.45	$108.40
Purchase #2	$80.53	11.519%	$89.8063	$89.81	$89.80	$89.80
Purchase #3	$105.76	11.808%	$118.2481	$118.25	$118.25	$118.20
Purchase #4	$195.93	7.870%	$211.3497	$211.35	$211.35	$211.30
Purchase #5	$220.47	4.478%	$230.3426	$230.34	$230.35	$230.30
Purchase #6	$86.25	8.845%	$93.8788	$93.88	$93.90	$93.90
Purchase #7	$238.64	11.666%	$266.4797	$266.48	$266.50	$266.50
7 purchase totals =	$1,031.41		$1,118.5369	$1,118.54	$1,118.60	$1,118.40