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	$81.82	8.796%	$89.0169	$89.02	$89.00	$89.00
Purchase #2	$92.65	11.559%	$103.3594	$103.36	$103.35	$103.40
Purchase #3	$208.53	3.258%	$215.3239	$215.32	$215.30	$215.30
Purchase #4	$239.27	7.317%	$256.7774	$256.78	$256.80	$256.80
Purchase #5	$52.72	5.374%	$55.5532	$55.55	$55.55	$55.60
Purchase #6	$109.50	6.306%	$116.4051	$116.41	$116.40	$116.40
Purchase #7	$220.61	5.154%	$231.9802	$231.98	$232.00	$232.00
7 purchase totals =	$1,005.10		$1,068.4161	$1,068.42	$1,068.40	$1,068.50