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	$49.50	6.825%	$52.8784	$52.88	$52.90	$52.90
Purchase #2	$182.39	13.122%	$206.3232	$206.32	$206.30	$206.30
Purchase #3	$237.52	3.522%	$245.8855	$245.89	$245.90	$245.90
Purchase #4	$55.65	12.825%	$62.7871	$62.79	$62.80	$62.80
Purchase #5	$151.81	6.320%	$161.4044	$161.40	$161.40	$161.40
Purchase #6	$172.62	3.857%	$179.278	$179.28	$179.30	$179.30
Purchase #7	$123.94	6.162%	$131.5772	$131.58	$131.60	$131.60
7 purchase totals =	$973.43		$1,040.1338	$1,040.14	$1,040.20	$1,040.20