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	$140.75	10.135%	$155.015	$155.02	$155.00	$155.00
Purchase #2	$102.99	8.593%	$111.8399	$111.84	$111.85	$111.80
Purchase #3	$66.38	8.627%	$72.1066	$72.11	$72.10	$72.10
Purchase #4	$108.77	7.673%	$117.1159	$117.12	$117.10	$117.10
Purchase #5	$40.54	5.339%	$42.7044	$42.70	$42.70	$42.70
Purchase #6	$184.62	6.676%	$196.9452	$196.95	$196.95	$196.90
Purchase #7	$51.86	9.226%	$56.6446	$56.64	$56.65	$56.60
7 purchase totals =	$695.91		$752.3716	$752.38	$752.35	$752.20