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	$244.37	3.873%	$253.8345	$253.83	$253.85	$253.80
Purchase #2	$99.68	7.803%	$107.458	$107.46	$107.45	$107.50
Purchase #3	$150.76	5.855%	$159.587	$159.59	$159.60	$159.60
Purchase #4	$67.75	6.226%	$71.9681	$71.97	$71.95	$72.00
Purchase #5	$205.52	7.741%	$221.4293	$221.43	$221.45	$221.40
Purchase #6	$81.34	9.475%	$89.047	$89.05	$89.05	$89.00
Purchase #7	$107.48	6.466%	$114.4297	$114.43	$114.45	$114.40
7 purchase totals =	$956.90		$1,017.7536	$1,017.76	$1,017.80	$1,017.70