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	$203.37	7.427%	$218.4743	$218.47	$218.45	$218.50
Purchase #2	$179.38	3.782%	$186.1642	$186.16	$186.15	$186.20
Purchase #3	$203.56	6.847%	$217.4978	$217.50	$217.50	$217.50
Purchase #4	$51.49	9.473%	$56.3676	$56.37	$56.35	$56.40
Purchase #5	$52.62	13.682%	$59.8195	$59.82	$59.80	$59.80
Purchase #6	$29.46	11.186%	$32.7554	$32.76	$32.75	$32.80
Purchase #7	$242.63	5.170%	$255.174	$255.17	$255.15	$255.20
7 purchase totals =	$962.51		$1,026.2528	$1,026.25	$1,026.15	$1,026.40