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	$220.90	11.192%	$245.6231	$245.62	$245.60	$245.60
Purchase #2	$88.64	6.108%	$94.0541	$94.05	$94.05	$94.10
Purchase #3	$213.36	4.115%	$222.1398	$222.14	$222.15	$222.10
Purchase #4	$80.46	6.764%	$85.9023	$85.90	$85.90	$85.90
Purchase #5	$186.77	4.241%	$194.6909	$194.69	$194.70	$194.70
Purchase #6	$103.57	5.792%	$109.5688	$109.57	$109.55	$109.60
Purchase #7	$41.37	5.319%	$43.5705	$43.57	$43.55	$43.60
7 purchase totals =	$935.07		$995.5495	$995.54	$995.50	$995.60