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	$232.78	11.622%	$259.8337	$259.83	$259.85	$259.80
Purchase #2	$80.40	4.354%	$83.9006	$83.90	$83.90	$83.90
Purchase #3	$213.67	8.368%	$231.5499	$231.55	$231.55	$231.50
Purchase #4	$247.30	12.552%	$278.3411	$278.34	$278.35	$278.30
Purchase #5	$102.66	3.137%	$105.8804	$105.88	$105.90	$105.90
Purchase #6	$26.74	7.124%	$28.645	$28.65	$28.65	$28.60
Purchase #7	$155.41	7.409%	$166.9243	$166.92	$166.90	$166.90
7 purchase totals =	$1,058.96		$1,155.0750	$1,155.07	$1,155.10	$1,154.90