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	$162.72	11.810%	$181.9372	$181.94	$181.95	$181.90
Purchase #2	$67.56	4.527%	$70.6184	$70.62	$70.60	$70.60
Purchase #3	$119.43	3.730%	$123.8847	$123.88	$123.90	$123.90
Purchase #4	$182.30	7.670%	$196.2824	$196.28	$196.30	$196.30
Purchase #5	$42.48	12.725%	$47.8856	$47.89	$47.90	$47.90
Purchase #6	$100.69	6.642%	$107.3778	$107.38	$107.40	$107.40
Purchase #7	$57.48	10.157%	$63.3182	$63.32	$63.30	$63.30
7 purchase totals =	$732.66		$791.3043	$791.31	$791.35	$791.30