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	$221.82	13.550%	$251.8766	$251.88	$251.90	$251.90
Purchase #2	$196.90	5.287%	$207.3101	$207.31	$207.30	$207.30
Purchase #3	$134.50	12.863%	$151.8007	$151.80	$151.80	$151.80
Purchase #4	$186.56	7.559%	$200.6621	$200.66	$200.65	$200.70
Purchase #5	$36.84	13.575%	$41.841	$41.84	$41.85	$41.80
Purchase #6	$91.80	12.654%	$103.4164	$103.42	$103.40	$103.40
Purchase #7	$193.27	7.415%	$207.601	$207.60	$207.60	$207.60
7 purchase totals =	$1,061.69		$1,164.5079	$1,164.51	$1,164.50	$1,164.50