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	$38.41	11.247%	$42.73	$42.73	$42.75	$42.70
Purchase #2	$175.75	11.610%	$196.1546	$196.15	$196.15	$196.20
Purchase #3	$143.28	6.713%	$152.8984	$152.90	$152.90	$152.90
Purchase #4	$145.62	4.549%	$152.2443	$152.24	$152.25	$152.20
Purchase #5	$211.78	8.791%	$230.3976	$230.40	$230.40	$230.40
Purchase #6	$52.64	5.214%	$55.3846	$55.38	$55.40	$55.40
Purchase #7	$99.44	12.637%	$112.0062	$112.01	$112.00	$112.00
7 purchase totals =	$866.92		$941.8157	$941.81	$941.85	$941.80