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	$130.33	7.518%	$140.1282	$140.13	$140.15	$140.10
Purchase #2	$10.48	3.271%	$10.8228	$10.82	$10.80	$10.80
Purchase #3	$186.98	4.864%	$196.0747	$196.07	$196.05	$196.10
Purchase #4	$25.65	7.870%	$27.6687	$27.67	$27.65	$27.70
Purchase #5	$213.60	6.171%	$226.7813	$226.78	$226.80	$226.80
Purchase #6	$225.55	13.260%	$255.4579	$255.46	$255.45	$255.50
Purchase #7	$58.71	4.584%	$61.4013	$61.40	$61.40	$61.40
7 purchase totals =	$851.30		$918.3349	$918.33	$918.30	$918.40