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	$122.28	4.562%	$127.8584	$127.86	$127.85	$127.90
Purchase #2	$175.68	5.788%	$185.8484	$185.85	$185.85	$185.80
Purchase #3	$224.37	3.349%	$231.8842	$231.88	$231.90	$231.90
Purchase #4	$106.54	4.614%	$111.4558	$111.46	$111.45	$111.50
Purchase #5	$30.82	7.392%	$33.0982	$33.10	$33.10	$33.10
Purchase #6	$45.32	4.668%	$47.4355	$47.44	$47.45	$47.40
Purchase #7	$184.90	6.267%	$196.4877	$196.49	$196.50	$196.50
7 purchase totals =	$889.91		$934.0682	$934.08	$934.10	$934.10