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	$82.78	9.774%	$90.8709	$90.87	$90.85	$90.90
Purchase #2	$212.26	5.453%	$223.8345	$223.83	$223.85	$223.80
Purchase #3	$122.48	12.577%	$137.8843	$137.88	$137.90	$137.90
Purchase #4	$249.67	7.555%	$268.5326	$268.53	$268.55	$268.50
Purchase #5	$82.26	11.522%	$91.738	$91.74	$91.75	$91.70
Purchase #6	$186.32	4.707%	$195.0901	$195.09	$195.10	$195.10
Purchase #7	$173.40	3.643%	$179.717	$179.72	$179.70	$179.70
7 purchase totals =	$1,109.17		$1,187.6674	$1,187.66	$1,187.70	$1,187.60