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	$234.62	7.772%	$252.8547	$252.85	$252.85	$252.90
Purchase #2	$142.53	6.135%	$151.2742	$151.27	$151.25	$151.30
Purchase #3	$37.78	8.412%	$40.9581	$40.96	$40.95	$41.00
Purchase #4	$119.92	6.262%	$127.4294	$127.43	$127.45	$127.40
Purchase #5	$132.66	6.705%	$141.5549	$141.55	$141.55	$141.60
Purchase #6	$81.53	5.414%	$85.944	$85.94	$85.95	$85.90
Purchase #7	$85.67	11.280%	$95.3336	$95.33	$95.35	$95.30
7 purchase totals =	$834.71		$895.3489	$895.33	$895.35	$895.40