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	$188.32	4.211%	$196.2502	$196.25	$196.25	$196.30
Purchase #2	$56.75	7.526%	$61.021	$61.02	$61.00	$61.00
Purchase #3	$49.42	4.348%	$51.5688	$51.57	$51.55	$51.60
Purchase #4	$106.75	4.859%	$111.937	$111.94	$111.95	$111.90
Purchase #5	$20.88	12.319%	$23.4522	$23.45	$23.45	$23.50
Purchase #6	$177.36	12.372%	$199.303	$199.30	$199.30	$199.30
Purchase #7	$167.62	10.630%	$185.438	$185.44	$185.45	$185.40
7 purchase totals =	$767.10		$828.9702	$828.97	$828.95	$829.00