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	$80.58	12.680%	$90.7975	$90.80	$90.80	$90.80
Purchase #2	$182.89	5.351%	$192.6764	$192.68	$192.70	$192.70
Purchase #3	$139.85	5.765%	$147.9124	$147.91	$147.90	$147.90
Purchase #4	$213.59	7.654%	$229.9382	$229.94	$229.95	$229.90
Purchase #5	$11.73	6.398%	$12.4805	$12.48	$12.50	$12.50
Purchase #6	$143.55	5.277%	$151.1251	$151.13	$151.15	$151.10
Purchase #7	$209.93	5.620%	$221.7281	$221.73	$221.75	$221.70
7 purchase totals =	$982.12		$1,046.6582	$1,046.67	$1,046.75	$1,046.60