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	$194.45	5.377%	$204.9056	$204.91	$204.90	$204.90
Purchase #2	$75.56	7.831%	$81.4771	$81.48	$81.50	$81.50
Purchase #3	$20.44	3.551%	$21.1658	$21.17	$21.15	$21.20
Purchase #4	$88.38	12.304%	$99.2543	$99.25	$99.25	$99.30
Purchase #5	$7.95	6.241%	$8.4462	$8.45	$8.45	$8.40
Purchase #6	$81.85	13.730%	$93.088	$93.09	$93.10	$93.10
Purchase #7	$92.82	7.205%	$99.5077	$99.51	$99.50	$99.50
7 purchase totals =	$561.45		$607.8447	$607.86	$607.85	$607.90