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	$242.37	4.699%	$253.759	$253.76	$253.75	$253.80
Purchase #2	$77.45	8.489%	$84.0247	$84.02	$84.00	$84.00
Purchase #3	$154.97	9.395%	$169.5294	$169.53	$169.55	$169.50
Purchase #4	$72.91	7.242%	$78.1901	$78.19	$78.20	$78.20
Purchase #5	$38.71	8.123%	$41.8544	$41.85	$41.85	$41.90
Purchase #6	$107.78	3.550%	$111.6062	$111.61	$111.60	$111.60
Purchase #7	$106.41	5.693%	$112.4679	$112.47	$112.45	$112.50
7 purchase totals =	$800.60		$851.4317	$851.43	$851.40	$851.50