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	$54.66	8.593%	$59.3569	$59.36	$59.35	$59.40
Purchase #2	$115.47	9.665%	$126.6302	$126.63	$126.65	$126.60
Purchase #3	$7.78	8.746%	$8.4604	$8.46	$8.45	$8.50
Purchase #4	$8.83	6.361%	$9.3917	$9.39	$9.40	$9.40
Purchase #5	$68.41	6.535%	$72.8806	$72.88	$72.90	$72.90
Purchase #6	$112.89	13.243%	$127.84	$127.84	$127.85	$127.80
Purchase #7	$148.45	11.446%	$165.4416	$165.44	$165.45	$165.40
7 purchase totals =	$516.49		$570.0014	$570.00	$570.05	$570.00