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	$186.45	11.621%	$208.1174	$208.12	$208.10	$208.10
Purchase #2	$112.34	11.681%	$125.4624	$125.46	$125.45	$125.50
Purchase #3	$161.72	4.237%	$168.5721	$168.57	$168.55	$168.60
Purchase #4	$17.55	3.817%	$18.2199	$18.22	$18.20	$18.20
Purchase #5	$78.27	5.454%	$82.5388	$82.54	$82.55	$82.50
Purchase #6	$219.97	13.602%	$249.8903	$249.89	$249.90	$249.90
Purchase #7	$30.46	7.666%	$32.7951	$32.80	$32.80	$32.80
7 purchase totals =	$806.76		$885.5960	$885.60	$885.55	$885.60