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	$160.26	13.495%	$181.8871	$181.89	$181.90	$181.90
Purchase #2	$10.64	7.570%	$11.4454	$11.45	$11.45	$11.40
Purchase #3	$35.78	3.801%	$37.14	$37.14	$37.15	$37.10
Purchase #4	$139.86	7.681%	$150.6026	$150.60	$150.60	$150.60
Purchase #5	$41.78	5.323%	$44.0039	$44.00	$44.00	$44.00
Purchase #6	$85.92	4.704%	$89.9617	$89.96	$89.95	$90.00
Purchase #7	$154.67	12.768%	$174.4183	$174.42	$174.40	$174.40
7 purchase totals =	$628.91		$689.4590	$689.46	$689.45	$689.40