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	$163.46	3.608%	$169.3576	$169.36	$169.35	$169.40
Purchase #2	$172.42	3.836%	$179.034	$179.03	$179.05	$179.00
Purchase #3	$112.66	12.566%	$126.8169	$126.82	$126.80	$126.80
Purchase #4	$75.97	3.230%	$78.4238	$78.42	$78.40	$78.40
Purchase #5	$68.39	5.115%	$71.8881	$71.89	$71.90	$71.90
Purchase #6	$174.98	10.654%	$193.6224	$193.62	$193.60	$193.60
Purchase #7	$134.45	11.816%	$150.3366	$150.34	$150.35	$150.30
7 purchase totals =	$902.33		$969.4794	$969.48	$969.45	$969.40