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	$94.47	7.331%	$101.3956	$101.40	$101.40	$101.40
Purchase #2	$177.89	3.822%	$184.689	$184.69	$184.70	$184.70
Purchase #3	$96.73	7.451%	$103.9374	$103.94	$103.95	$103.90
Purchase #4	$44.40	6.794%	$47.4165	$47.42	$47.40	$47.40
Purchase #5	$125.50	9.135%	$136.9644	$136.96	$136.95	$137.00
Purchase #6	$73.55	9.471%	$80.5159	$80.52	$80.50	$80.50
Purchase #7	$40.64	12.668%	$45.7883	$45.79	$45.80	$45.80
7 purchase totals =	$653.18		$700.7071	$700.72	$700.70	$700.70