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	$231.50	4.154%	$241.1165	$241.12	$241.10	$241.10
Purchase #2	$159.45	12.420%	$179.2537	$179.25	$179.25	$179.30
Purchase #3	$234.90	6.684%	$250.6007	$250.60	$250.60	$250.60
Purchase #4	$35.45	6.250%	$37.6656	$37.67	$37.65	$37.70
Purchase #5	$90.72	12.668%	$102.2124	$102.21	$102.20	$102.20
Purchase #6	$127.58	4.304%	$133.071	$133.07	$133.05	$133.10
Purchase #7	$211.82	4.116%	$220.5385	$220.54	$220.55	$220.50
7 purchase totals =	$1,091.42		$1,164.4584	$1,164.46	$1,164.40	$1,164.50