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	$67.63	4.561%	$70.7146	$70.71	$70.70	$70.70
Purchase #2	$123.39	3.208%	$127.3484	$127.35	$127.35	$127.30
Purchase #3	$50.38	11.830%	$56.34	$56.34	$56.35	$56.30
Purchase #4	$164.57	8.386%	$178.3708	$178.37	$178.35	$178.40
Purchase #5	$72.63	5.363%	$76.5251	$76.53	$76.55	$76.50
Purchase #6	$121.71	4.604%	$127.3135	$127.31	$127.30	$127.30
Purchase #7	$115.25	11.495%	$128.498	$128.50	$128.50	$128.50
7 purchase totals =	$715.56		$765.1104	$765.11	$765.10	$765.00