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	$180.98	8.557%	$196.4665	$196.47	$196.45	$196.50
Purchase #2	$184.89	8.446%	$200.5058	$200.51	$200.50	$200.50
Purchase #3	$60.66	10.601%	$67.0906	$67.09	$67.10	$67.10
Purchase #4	$137.89	13.798%	$156.9161	$156.92	$156.90	$156.90
Purchase #5	$234.59	4.597%	$245.3741	$245.37	$245.35	$245.40
Purchase #6	$218.26	12.286%	$245.0754	$245.08	$245.10	$245.10
Purchase #7	$245.74	3.586%	$254.5522	$254.55	$254.55	$254.60
7 purchase totals =	$1,263.01		$1,365.9807	$1,365.99	$1,365.95	$1,366.10