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	$211.75	3.533%	$219.2311	$219.23	$219.25	$219.20
Purchase #2	$107.39	3.631%	$111.2893	$111.29	$111.30	$111.30
Purchase #3	$79.94	13.507%	$90.7375	$90.74	$90.75	$90.70
Purchase #4	$138.81	12.386%	$156.003	$156.00	$156.00	$156.00
Purchase #5	$84.66	12.535%	$95.2721	$95.27	$95.25	$95.30
Purchase #6	$19.57	11.533%	$21.827	$21.83	$21.85	$21.80
Purchase #7	$129.33	9.629%	$141.7832	$141.78	$141.80	$141.80
7 purchase totals =	$771.45		$836.1432	$836.14	$836.20	$836.10