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	$243.78	9.232%	$266.2858	$266.29	$266.30	$266.30
Purchase #2	$197.81	10.775%	$219.124	$219.12	$219.10	$219.10
Purchase #3	$245.50	5.171%	$258.1948	$258.19	$258.20	$258.20
Purchase #4	$74.45	5.765%	$78.742	$78.74	$78.75	$78.70
Purchase #5	$55.97	8.193%	$60.5556	$60.56	$60.55	$60.60
Purchase #6	$105.27	12.746%	$118.6877	$118.69	$118.70	$118.70
Purchase #7	$56.91	4.430%	$59.4311	$59.43	$59.45	$59.40
7 purchase totals =	$979.69		$1,061.0210	$1,061.02	$1,061.05	$1,061.00