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	$245.69	8.242%	$265.9398	$265.94	$265.95	$265.90
Purchase #2	$20.33	7.576%	$21.8702	$21.87	$21.85	$21.90
Purchase #3	$108.92	8.288%	$117.9473	$117.95	$117.95	$117.90
Purchase #4	$66.58	10.444%	$73.5336	$73.53	$73.55	$73.50
Purchase #5	$157.48	5.355%	$165.9131	$165.91	$165.90	$165.90
Purchase #6	$141.43	7.697%	$152.3159	$152.32	$152.30	$152.30
Purchase #7	$203.57	3.830%	$211.3667	$211.37	$211.35	$211.40
7 purchase totals =	$944.00		$1,008.8866	$1,008.89	$1,008.85	$1,008.80