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	$98.29	13.613%	$111.6702	$111.67	$111.65	$111.70
Purchase #2	$132.90	13.150%	$150.3764	$150.38	$150.40	$150.40
Purchase #3	$88.72	8.464%	$96.2293	$96.23	$96.25	$96.20
Purchase #4	$93.78	6.590%	$99.9601	$99.96	$99.95	$100.00
Purchase #5	$7.89	8.395%	$8.5524	$8.55	$8.55	$8.60
Purchase #6	$219.40	3.618%	$227.3379	$227.34	$227.35	$227.30
Purchase #7	$80.76	12.797%	$91.0949	$91.09	$91.10	$91.10
7 purchase totals =	$721.74		$785.2212	$785.22	$785.25	$785.30