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	$147.96	5.139%	$155.5637	$155.56	$155.55	$155.60
Purchase #2	$136.94	6.848%	$146.3177	$146.32	$146.30	$146.30
Purchase #3	$164.43	6.364%	$174.8943	$174.89	$174.90	$174.90
Purchase #4	$133.94	10.825%	$148.439	$148.44	$148.45	$148.40
Purchase #5	$131.73	4.304%	$137.3997	$137.40	$137.40	$137.40
Purchase #6	$131.46	12.172%	$147.4613	$147.46	$147.45	$147.50
Purchase #7	$244.73	12.324%	$274.8905	$274.89	$274.90	$274.90
7 purchase totals =	$1,091.19		$1,184.9662	$1,184.96	$1,184.95	$1,185.00