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	$146.83	9.710%	$161.0872	$161.09	$161.10	$161.10
Purchase #2	$248.51	5.740%	$262.7745	$262.77	$262.75	$262.80
Purchase #3	$249.30	6.609%	$265.7762	$265.78	$265.80	$265.80
Purchase #4	$62.92	5.751%	$66.5385	$66.54	$66.55	$66.50
Purchase #5	$185.72	11.470%	$207.0221	$207.02	$207.00	$207.00
Purchase #6	$109.32	4.804%	$114.5717	$114.57	$114.55	$114.60
Purchase #7	$80.65	11.389%	$89.8352	$89.84	$89.85	$89.80
7 purchase totals =	$1,083.25		$1,167.6054	$1,167.61	$1,167.60	$1,167.60