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	$68.79	11.135%	$76.4498	$76.45	$76.45	$76.40
Purchase #2	$55.64	7.637%	$59.8892	$59.89	$59.90	$59.90
Purchase #3	$81.70	10.830%	$90.5481	$90.55	$90.55	$90.50
Purchase #4	$167.57	13.265%	$189.7982	$189.80	$189.80	$189.80
Purchase #5	$173.69	6.866%	$185.6156	$185.62	$185.60	$185.60
Purchase #6	$212.88	3.153%	$219.5921	$219.59	$219.60	$219.60
Purchase #7	$250.73	3.728%	$260.0772	$260.08	$260.10	$260.10
7 purchase totals =	$1,011.00		$1,081.9702	$1,081.98	$1,082.00	$1,081.90