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	$161.83	6.606%	$172.5205	$172.52	$172.50	$172.50
Purchase #2	$156.92	6.148%	$166.5674	$166.57	$166.55	$166.60
Purchase #3	$43.76	3.665%	$45.3638	$45.36	$45.35	$45.40
Purchase #4	$98.78	8.447%	$107.1239	$107.12	$107.10	$107.10
Purchase #5	$126.98	12.389%	$142.7116	$142.71	$142.70	$142.70
Purchase #6	$250.71	4.466%	$261.9067	$261.91	$261.90	$261.90
Purchase #7	$108.51	6.644%	$115.7194	$115.72	$115.70	$115.70
7 purchase totals =	$947.49		$1,011.9133	$1,011.91	$1,011.80	$1,011.90