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	$187.85	6.451%	$199.9682	$199.97	$199.95	$200.00
Purchase #2	$47.26	9.835%	$51.908	$51.91	$51.90	$51.90
Purchase #3	$89.29	11.306%	$99.3851	$99.39	$99.40	$99.40
Purchase #4	$95.27	4.276%	$99.3437	$99.34	$99.35	$99.30
Purchase #5	$196.33	7.543%	$211.1392	$211.14	$211.15	$211.10
Purchase #6	$118.56	3.291%	$122.4618	$122.46	$122.45	$122.50
Purchase #7	$86.81	6.326%	$92.3016	$92.30	$92.30	$92.30
7 purchase totals =	$821.37		$876.5076	$876.51	$876.50	$876.50