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	$170.90	9.548%	$187.2175	$187.22	$187.20	$187.20
Purchase #2	$161.42	12.337%	$181.3344	$181.33	$181.35	$181.30
Purchase #3	$44.52	7.839%	$48.0099	$48.01	$48.00	$48.00
Purchase #4	$30.72	6.151%	$32.6096	$32.61	$32.60	$32.60
Purchase #5	$30.96	8.631%	$33.6322	$33.63	$33.65	$33.60
Purchase #6	$167.37	4.533%	$174.9569	$174.96	$174.95	$175.00
Purchase #7	$115.76	11.336%	$128.8826	$128.88	$128.90	$128.90
7 purchase totals =	$721.65		$786.6431	$786.64	$786.65	$786.60