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	$53.27	9.422%	$58.2891	$58.29	$58.30	$58.30
Purchase #2	$201.26	4.783%	$210.8863	$210.89	$210.90	$210.90
Purchase #3	$142.72	8.672%	$155.0967	$155.10	$155.10	$155.10
Purchase #4	$16.90	4.737%	$17.7006	$17.70	$17.70	$17.70
Purchase #5	$33.72	11.368%	$37.5533	$37.55	$37.55	$37.60
Purchase #6	$55.72	7.478%	$59.8867	$59.89	$59.90	$59.90
Purchase #7	$245.68	8.392%	$266.2975	$266.30	$266.30	$266.30
7 purchase totals =	$749.27		$805.7102	$805.72	$805.75	$805.80