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	$242.59	13.864%	$276.2227	$276.22	$276.20	$276.20
Purchase #2	$166.35	12.755%	$187.5679	$187.57	$187.55	$187.60
Purchase #3	$65.65	13.355%	$74.4176	$74.42	$74.40	$74.40
Purchase #4	$248.90	11.380%	$277.2248	$277.22	$277.20	$277.20
Purchase #5	$165.72	3.486%	$171.497	$171.50	$171.50	$171.50
Purchase #6	$33.78	5.609%	$35.6747	$35.67	$35.65	$35.70
Purchase #7	$36.90	9.537%	$40.4192	$40.42	$40.40	$40.40
7 purchase totals =	$959.89		$1,063.0239	$1,063.02	$1,062.90	$1,063.00