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	$81.67	5.174%	$85.8956	$85.90	$85.90	$85.90
Purchase #2	$133.95	5.614%	$141.47	$141.47	$141.45	$141.50
Purchase #3	$41.91	7.562%	$45.0792	$45.08	$45.10	$45.10
Purchase #4	$166.89	3.542%	$172.8012	$172.80	$172.80	$172.80
Purchase #5	$128.61	10.768%	$142.4587	$142.46	$142.45	$142.50
Purchase #6	$236.39	5.682%	$249.8217	$249.82	$249.80	$249.80
Purchase #7	$191.99	12.534%	$216.054	$216.05	$216.05	$216.10
7 purchase totals =	$981.41		$1,053.5804	$1,053.58	$1,053.55	$1,053.70