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	$127.57	3.417%	$131.9291	$131.93	$131.95	$131.90
Purchase #2	$156.46	4.646%	$163.7291	$163.73	$163.75	$163.70
Purchase #3	$72.78	9.551%	$79.7312	$79.73	$79.75	$79.70
Purchase #4	$32.93	12.421%	$37.0202	$37.02	$37.00	$37.00
Purchase #5	$227.69	12.624%	$256.4336	$256.43	$256.45	$256.40
Purchase #6	$219.83	11.558%	$245.238	$245.24	$245.25	$245.20
Purchase #7	$156.98	3.456%	$162.4052	$162.41	$162.40	$162.40
7 purchase totals =	$994.24		$1,076.4864	$1,076.49	$1,076.55	$1,076.30