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	$141.88	10.285%	$156.4724	$156.47	$156.45	$156.50
Purchase #2	$94.69	9.441%	$103.6297	$103.63	$103.65	$103.60
Purchase #3	$22.54	11.187%	$25.0615	$25.06	$25.05	$25.10
Purchase #4	$105.76	3.641%	$109.6107	$109.61	$109.60	$109.60
Purchase #5	$115.48	13.762%	$131.3724	$131.37	$131.35	$131.40
Purchase #6	$86.73	4.364%	$90.5149	$90.51	$90.50	$90.50
Purchase #7	$117.66	10.835%	$130.4085	$130.41	$130.40	$130.40
7 purchase totals =	$684.74		$747.0701	$747.06	$747.00	$747.10