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	$174.36	12.429%	$196.0312	$196.03	$196.05	$196.00
Purchase #2	$88.97	12.800%	$100.3582	$100.36	$100.35	$100.40
Purchase #3	$197.57	13.345%	$223.9357	$223.94	$223.95	$223.90
Purchase #4	$92.86	4.563%	$97.0972	$97.10	$97.10	$97.10
Purchase #5	$74.26	10.776%	$82.2623	$82.26	$82.25	$82.30
Purchase #6	$81.63	5.216%	$85.8878	$85.89	$85.90	$85.90
Purchase #7	$63.33	13.683%	$71.9954	$72.00	$72.00	$72.00
7 purchase totals =	$772.98		$857.5678	$857.58	$857.60	$857.60