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	$186.55	11.674%	$208.3278	$208.33	$208.35	$208.30
Purchase #2	$24.98	13.272%	$28.2953	$28.30	$28.30	$28.30
Purchase #3	$225.52	13.433%	$255.8141	$255.81	$255.80	$255.80
Purchase #4	$72.89	10.737%	$80.7162	$80.72	$80.70	$80.70
Purchase #5	$212.39	11.512%	$236.8403	$236.84	$236.85	$236.80
Purchase #6	$171.94	10.341%	$189.7203	$189.72	$189.70	$189.70
Purchase #7	$40.68	11.667%	$45.4261	$45.43	$45.45	$45.40
7 purchase totals =	$934.95		$1,045.1401	$1,045.15	$1,045.15	$1,045.00