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	$116.50	9.854%	$127.9799	$127.98	$128.00	$128.00
Purchase #2	$39.83	8.851%	$43.3554	$43.36	$43.35	$43.40
Purchase #3	$157.79	13.744%	$179.4767	$179.48	$179.50	$179.50
Purchase #4	$71.86	9.285%	$78.5322	$78.53	$78.55	$78.50
Purchase #5	$33.83	11.607%	$37.7566	$37.76	$37.75	$37.80
Purchase #6	$239.29	11.131%	$265.9254	$265.93	$265.95	$265.90
Purchase #7	$245.47	10.395%	$270.9866	$270.99	$271.00	$271.00
7 purchase totals =	$904.57		$1,004.0128	$1,004.03	$1,004.10	$1,004.10