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	$8.38	10.486%	$9.2587	$9.26	$9.25	$9.30
Purchase #2	$210.43	9.826%	$231.1069	$231.11	$231.10	$231.10
Purchase #3	$162.58	10.119%	$179.0315	$179.03	$179.05	$179.00
Purchase #4	$37.37	10.139%	$41.1589	$41.16	$41.15	$41.20
Purchase #5	$53.30	11.807%	$59.5931	$59.59	$59.60	$59.60
Purchase #6	$166.42	3.274%	$171.8686	$171.87	$171.85	$171.90
Purchase #7	$222.42	7.298%	$238.6522	$238.65	$238.65	$238.70
7 purchase totals =	$860.90		$930.6699	$930.67	$930.65	$930.80