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	$68.31	6.422%	$72.6969	$72.70	$72.70	$72.70
Purchase #2	$23.28	9.273%	$25.4388	$25.44	$25.45	$25.40
Purchase #3	$181.54	4.327%	$189.3952	$189.40	$189.40	$189.40
Purchase #4	$211.70	4.637%	$221.5165	$221.52	$221.50	$221.50
Purchase #5	$127.27	3.535%	$131.769	$131.77	$131.75	$131.80
Purchase #6	$19.70	6.105%	$20.9027	$20.90	$20.90	$20.90
Purchase #7	$40.36	4.840%	$42.3134	$42.31	$42.30	$42.30
7 purchase totals =	$672.16		$704.0325	$704.04	$704.00	$704.00