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	$176.96	11.479%	$197.2732	$197.27	$197.25	$197.30
Purchase #2	$243.51	11.189%	$270.7563	$270.76	$270.75	$270.80
Purchase #3	$119.72	9.759%	$131.4035	$131.40	$131.40	$131.40
Purchase #4	$64.91	9.452%	$71.0453	$71.05	$71.05	$71.00
Purchase #5	$39.88	9.175%	$43.539	$43.54	$43.55	$43.50
Purchase #6	$95.98	10.341%	$105.9053	$105.91	$105.90	$105.90
Purchase #7	$177.60	11.275%	$197.6244	$197.62	$197.60	$197.60
7 purchase totals =	$918.56		$1,017.5470	$1,017.55	$1,017.50	$1,017.50