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	$134.95	5.518%	$142.3965	$142.40	$142.40	$142.40
Purchase #2	$29.60	6.191%	$31.4325	$31.43	$31.45	$31.40
Purchase #3	$209.88	12.494%	$236.1024	$236.10	$236.10	$236.10
Purchase #4	$177.48	9.597%	$194.5128	$194.51	$194.50	$194.50
Purchase #5	$76.37	3.340%	$78.9208	$78.92	$78.90	$78.90
Purchase #6	$68.55	11.642%	$76.5306	$76.53	$76.55	$76.50
Purchase #7	$150.89	13.819%	$171.7415	$171.74	$171.75	$171.70
7 purchase totals =	$847.72		$931.6371	$931.63	$931.65	$931.50