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	$250.59	11.472%	$279.3377	$279.34	$279.35	$279.30
Purchase #2	$30.67	8.704%	$33.3395	$33.34	$33.35	$33.30
Purchase #3	$30.59	8.541%	$33.2027	$33.20	$33.20	$33.20
Purchase #4	$131.25	7.872%	$141.582	$141.58	$141.60	$141.60
Purchase #5	$249.68	5.680%	$263.8618	$263.86	$263.85	$263.90
Purchase #6	$157.95	10.413%	$174.3973	$174.40	$174.40	$174.40
Purchase #7	$148.75	5.495%	$156.9238	$156.92	$156.90	$156.90
7 purchase totals =	$999.48		$1,082.6448	$1,082.64	$1,082.65	$1,082.60