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	$49.58	9.584%	$54.3317	$54.33	$54.35	$54.30
Purchase #2	$205.36	3.683%	$212.9234	$212.92	$212.90	$212.90
Purchase #3	$184.79	6.475%	$196.7552	$196.76	$196.75	$196.80
Purchase #4	$32.78	13.198%	$37.1063	$37.11	$37.10	$37.10
Purchase #5	$237.43	7.659%	$255.6148	$255.61	$255.60	$255.60
Purchase #6	$78.66	13.415%	$89.2122	$89.21	$89.20	$89.20
Purchase #7	$98.78	13.554%	$112.1686	$112.17	$112.15	$112.20
7 purchase totals =	$887.38		$958.1122	$958.11	$958.05	$958.10