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	$119.36	6.282%	$126.8582	$126.86	$126.85	$126.90
Purchase #2	$178.54	10.119%	$196.6065	$196.61	$196.60	$196.60
Purchase #3	$52.63	10.778%	$58.3025	$58.30	$58.30	$58.30
Purchase #4	$135.72	7.511%	$145.9139	$145.91	$145.90	$145.90
Purchase #5	$70.66	11.608%	$78.8622	$78.86	$78.85	$78.90
Purchase #6	$178.72	12.281%	$200.6686	$200.67	$200.65	$200.70
Purchase #7	$76.71	5.126%	$80.6422	$80.64	$80.65	$80.60
7 purchase totals =	$812.34		$887.8541	$887.85	$887.80	$887.90