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	$181.49	9.588%	$198.8913	$198.89	$198.90	$198.90
Purchase #2	$136.31	4.828%	$142.891	$142.89	$142.90	$142.90
Purchase #3	$160.36	10.741%	$177.5843	$177.58	$177.60	$177.60
Purchase #4	$47.91	11.444%	$53.3928	$53.39	$53.40	$53.40
Purchase #5	$96.78	3.304%	$99.9776	$99.98	$100.00	$100.00
Purchase #6	$151.48	5.869%	$160.3704	$160.37	$160.35	$160.40
Purchase #7	$38.38	11.439%	$42.7703	$42.77	$42.75	$42.80
7 purchase totals =	$812.71		$875.8777	$875.87	$875.90	$876.00