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	$46.32	12.399%	$52.0632	$52.06	$52.05	$52.10
Purchase #2	$38.99	3.802%	$40.4724	$40.47	$40.45	$40.50
Purchase #3	$202.68	3.347%	$209.4637	$209.46	$209.45	$209.50
Purchase #4	$242.69	13.837%	$276.271	$276.27	$276.25	$276.30
Purchase #5	$218.67	5.382%	$230.4388	$230.44	$230.45	$230.40
Purchase #6	$62.37	6.551%	$66.4559	$66.46	$66.45	$66.50
Purchase #7	$198.41	5.462%	$209.2472	$209.25	$209.25	$209.20
7 purchase totals =	$1,010.13		$1,084.4122	$1,084.41	$1,084.35	$1,084.50