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	$203.83	4.172%	$212.3338	$212.33	$212.35	$212.30
Purchase #2	$184.49	8.592%	$200.3414	$200.34	$200.35	$200.30
Purchase #3	$148.74	13.580%	$168.9389	$168.94	$168.95	$168.90
Purchase #4	$94.80	10.327%	$104.59	$104.59	$104.60	$104.60
Purchase #5	$141.71	9.248%	$154.8153	$154.82	$154.80	$154.80
Purchase #6	$93.99	10.144%	$103.5243	$103.52	$103.50	$103.50
Purchase #7	$107.57	11.416%	$119.8502	$119.85	$119.85	$119.90
7 purchase totals =	$975.13		$1,064.3939	$1,064.39	$1,064.40	$1,064.30