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	$169.48	6.798%	$181.0013	$181.00	$181.00	$181.00
Purchase #2	$205.56	8.697%	$223.4376	$223.44	$223.45	$223.40
Purchase #3	$140.94	13.226%	$159.5807	$159.58	$159.60	$159.60
Purchase #4	$159.60	3.160%	$164.6434	$164.64	$164.65	$164.60
Purchase #5	$106.46	4.557%	$111.3114	$111.31	$111.30	$111.30
Purchase #6	$161.37	9.488%	$176.6808	$176.68	$176.70	$176.70
Purchase #7	$74.30	6.164%	$78.8799	$78.88	$78.90	$78.90
7 purchase totals =	$1,017.71		$1,095.5351	$1,095.53	$1,095.60	$1,095.50