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	$213.95	7.688%	$230.3985	$230.40	$230.40	$230.40
Purchase #2	$181.81	13.794%	$206.8889	$206.89	$206.90	$206.90
Purchase #3	$223.67	6.234%	$237.6136	$237.61	$237.60	$237.60
Purchase #4	$89.73	12.356%	$100.817	$100.82	$100.80	$100.80
Purchase #5	$22.79	3.450%	$23.5763	$23.58	$23.60	$23.60
Purchase #6	$196.31	10.298%	$216.526	$216.53	$216.55	$216.50
Purchase #7	$66.33	6.125%	$70.3927	$70.39	$70.40	$70.40
7 purchase totals =	$994.59		$1,086.2130	$1,086.22	$1,086.25	$1,086.20