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	$151.78	5.116%	$159.5451	$159.55	$159.55	$159.50
Purchase #2	$184.97	6.277%	$196.5806	$196.58	$196.60	$196.60
Purchase #3	$144.71	12.199%	$162.3632	$162.36	$162.35	$162.40
Purchase #4	$99.51	8.488%	$107.9564	$107.96	$107.95	$108.00
Purchase #5	$173.66	9.813%	$190.7013	$190.70	$190.70	$190.70
Purchase #6	$221.56	11.841%	$247.7949	$247.79	$247.80	$247.80
Purchase #7	$73.48	6.249%	$78.0718	$78.07	$78.05	$78.10
7 purchase totals =	$1,049.67		$1,143.0133	$1,143.01	$1,143.00	$1,143.10