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	$98.29	4.610%	$102.8212	$102.82	$102.80	$102.80
Purchase #2	$216.42	12.255%	$242.9423	$242.94	$242.95	$242.90
Purchase #3	$102.27	9.572%	$112.0593	$112.06	$112.05	$112.10
Purchase #4	$88.77	13.236%	$100.5196	$100.52	$100.50	$100.50
Purchase #5	$223.83	11.625%	$249.8502	$249.85	$249.85	$249.90
Purchase #6	$56.93	6.356%	$60.5485	$60.55	$60.55	$60.50
Purchase #7	$126.94	7.445%	$136.3907	$136.39	$136.40	$136.40
7 purchase totals =	$913.45		$1,005.1318	$1,005.13	$1,005.10	$1,005.10