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	$206.92	5.571%	$218.4475	$218.45	$218.45	$218.40
Purchase #2	$165.45	11.815%	$184.9979	$185.00	$185.00	$185.00
Purchase #3	$41.96	8.427%	$45.496	$45.50	$45.50	$45.50
Purchase #4	$171.82	6.553%	$183.0794	$183.08	$183.10	$183.10
Purchase #5	$71.51	7.163%	$76.6323	$76.63	$76.65	$76.60
Purchase #6	$139.26	12.354%	$156.4642	$156.46	$156.45	$156.50
Purchase #7	$69.89	13.757%	$79.5048	$79.50	$79.50	$79.50
7 purchase totals =	$866.81		$944.6221	$944.62	$944.65	$944.60