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	$212.36	13.311%	$240.6272	$240.63	$240.65	$240.60
Purchase #2	$65.90	10.384%	$72.7431	$72.74	$72.75	$72.70
Purchase #3	$238.84	7.588%	$256.9632	$256.96	$256.95	$257.00
Purchase #4	$176.57	11.167%	$196.2876	$196.29	$196.30	$196.30
Purchase #5	$180.62	6.229%	$191.8708	$191.87	$191.85	$191.90
Purchase #6	$16.44	11.571%	$18.3423	$18.34	$18.35	$18.30
Purchase #7	$32.76	5.538%	$34.5742	$34.57	$34.55	$34.60
7 purchase totals =	$923.49		$1,011.4084	$1,011.40	$1,011.40	$1,011.40