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	$92.54	11.854%	$103.5097	$103.51	$103.50	$103.50
Purchase #2	$85.42	3.731%	$88.607	$88.61	$88.60	$88.60
Purchase #3	$212.48	5.357%	$223.8626	$223.86	$223.85	$223.90
Purchase #4	$167.59	13.737%	$190.6118	$190.61	$190.60	$190.60
Purchase #5	$229.60	12.110%	$257.4046	$257.40	$257.40	$257.40
Purchase #6	$122.71	7.310%	$131.6801	$131.68	$131.70	$131.70
Purchase #7	$171.70	7.298%	$184.2307	$184.23	$184.25	$184.20
7 purchase totals =	$1,082.04		$1,179.9065	$1,179.90	$1,179.90	$1,179.90