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	$65.85	11.693%	$73.5498	$73.55	$73.55	$73.50
Purchase #2	$199.84	7.603%	$215.0338	$215.03	$215.05	$215.00
Purchase #3	$144.82	13.731%	$164.7052	$164.71	$164.70	$164.70
Purchase #4	$137.93	13.663%	$156.7754	$156.78	$156.80	$156.80
Purchase #5	$72.65	7.814%	$78.3269	$78.33	$78.35	$78.30
Purchase #6	$119.54	6.563%	$127.3854	$127.39	$127.40	$127.40
Purchase #7	$144.98	7.735%	$156.1942	$156.19	$156.20	$156.20
7 purchase totals =	$885.61		$971.9707	$971.98	$972.05	$971.90