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	$66.42	10.520%	$73.4074	$73.41	$73.40	$73.40
Purchase #2	$187.60	11.752%	$209.6468	$209.65	$209.65	$209.60
Purchase #3	$104.80	6.790%	$111.9159	$111.92	$111.90	$111.90
Purchase #4	$78.76	3.324%	$81.378	$81.38	$81.40	$81.40
Purchase #5	$32.71	11.548%	$36.4874	$36.49	$36.50	$36.50
Purchase #6	$104.94	9.595%	$115.009	$115.01	$115.00	$115.00
Purchase #7	$20.41	10.471%	$22.5471	$22.55	$22.55	$22.50
7 purchase totals =	$595.64		$650.3916	$650.41	$650.40	$650.30