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	$144.64	12.498%	$162.7171	$162.72	$162.70	$162.70
Purchase #2	$116.39	7.767%	$125.43	$125.43	$125.45	$125.40
Purchase #3	$49.43	11.462%	$55.0957	$55.10	$55.10	$55.10
Purchase #4	$54.82	6.752%	$58.5214	$58.52	$58.50	$58.50
Purchase #5	$172.56	4.620%	$180.5323	$180.53	$180.55	$180.50
Purchase #6	$155.50	5.860%	$164.6123	$164.61	$164.60	$164.60
Purchase #7	$172.94	12.175%	$193.9954	$194.00	$194.00	$194.00
7 purchase totals =	$866.28		$940.9042	$940.91	$940.90	$940.80