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	$174.84	3.731%	$181.3633	$181.36	$181.35	$181.40
Purchase #2	$179.42	10.750%	$198.7077	$198.71	$198.70	$198.70
Purchase #3	$20.67	5.369%	$21.7798	$21.78	$21.80	$21.80
Purchase #4	$105.31	5.618%	$111.2263	$111.23	$111.25	$111.20
Purchase #5	$137.81	7.127%	$147.6317	$147.63	$147.65	$147.60
Purchase #6	$250.91	9.396%	$274.4855	$274.49	$274.50	$274.50
Purchase #7	$33.52	11.866%	$37.4975	$37.50	$37.50	$37.50
7 purchase totals =	$902.48		$972.6918	$972.70	$972.75	$972.70