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	$186.48	5.493%	$196.7233	$196.72	$196.70	$196.70
Purchase #2	$22.94	4.313%	$23.9294	$23.93	$23.95	$23.90
Purchase #3	$81.70	11.222%	$90.8684	$90.87	$90.85	$90.90
Purchase #4	$159.33	10.116%	$175.4478	$175.45	$175.45	$175.40
Purchase #5	$69.55	11.323%	$77.4251	$77.43	$77.45	$77.40
Purchase #6	$76.36	12.808%	$86.1402	$86.14	$86.15	$86.10
Purchase #7	$198.32	6.529%	$211.2683	$211.27	$211.25	$211.30
7 purchase totals =	$794.68		$861.8025	$861.81	$861.80	$861.70