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	$109.27	7.546%	$117.5155	$117.52	$117.50	$117.50
Purchase #2	$14.26	11.405%	$15.8864	$15.89	$15.90	$15.90
Purchase #3	$62.37	6.657%	$66.522	$66.52	$66.50	$66.50
Purchase #4	$105.37	10.295%	$116.2178	$116.22	$116.20	$116.20
Purchase #5	$176.27	10.339%	$194.4946	$194.49	$194.50	$194.50
Purchase #6	$234.28	3.432%	$242.3205	$242.32	$242.30	$242.30
Purchase #7	$110.82	7.252%	$118.8567	$118.86	$118.85	$118.90
7 purchase totals =	$812.64		$871.8135	$871.82	$871.75	$871.80