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	$117.49	8.513%	$127.4919	$127.49	$127.50	$127.50
Purchase #2	$105.75	9.464%	$115.7582	$115.76	$115.75	$115.80
Purchase #3	$161.69	5.170%	$170.0494	$170.05	$170.05	$170.00
Purchase #4	$7.85	3.750%	$8.1444	$8.14	$8.15	$8.10
Purchase #5	$175.96	4.435%	$183.7638	$183.76	$183.75	$183.80
Purchase #6	$222.35	12.386%	$249.8903	$249.89	$249.90	$249.90
Purchase #7	$234.31	9.407%	$256.3515	$256.35	$256.35	$256.40
7 purchase totals =	$1,025.40		$1,111.4495	$1,111.44	$1,111.45	$1,111.50