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	$48.68	11.846%	$54.4466	$54.45	$54.45	$54.40
Purchase #2	$40.86	9.711%	$44.8279	$44.83	$44.85	$44.80
Purchase #3	$46.32	4.787%	$48.5373	$48.54	$48.55	$48.50
Purchase #4	$103.61	6.836%	$110.6928	$110.69	$110.70	$110.70
Purchase #5	$205.43	5.338%	$216.3959	$216.40	$216.40	$216.40
Purchase #6	$181.55	4.663%	$190.0157	$190.02	$190.00	$190.00
Purchase #7	$85.96	5.190%	$90.4213	$90.42	$90.40	$90.40
7 purchase totals =	$712.41		$755.3375	$755.35	$755.35	$755.20