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	$116.52	9.735%	$127.8632	$127.86	$127.85	$127.90
Purchase #2	$15.33	6.627%	$16.3459	$16.35	$16.35	$16.30
Purchase #3	$68.50	10.709%	$75.8357	$75.84	$75.85	$75.80
Purchase #4	$120.77	6.582%	$128.7191	$128.72	$128.70	$128.70
Purchase #5	$85.46	4.496%	$89.3023	$89.30	$89.30	$89.30
Purchase #6	$156.59	7.296%	$168.0148	$168.01	$168.00	$168.00
Purchase #7	$68.91	10.146%	$75.9016	$75.90	$75.90	$75.90
7 purchase totals =	$632.08		$681.9826	$681.98	$681.95	$681.90