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	$198.83	7.313%	$213.3704	$213.37	$213.35	$213.40
Purchase #2	$206.85	11.416%	$230.464	$230.46	$230.45	$230.50
Purchase #3	$19.61	4.111%	$20.4162	$20.42	$20.40	$20.40
Purchase #4	$185.54	6.139%	$196.9303	$196.93	$196.95	$196.90
Purchase #5	$198.76	3.406%	$205.5298	$205.53	$205.55	$205.50
Purchase #6	$39.71	6.866%	$42.4365	$42.44	$42.45	$42.40
Purchase #7	$125.99	4.323%	$131.4365	$131.44	$131.45	$131.40
7 purchase totals =	$975.29		$1,040.5837	$1,040.59	$1,040.60	$1,040.50