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	$168.46	5.401%	$177.5585	$177.56	$177.55	$177.60
Purchase #2	$187.52	13.752%	$213.3078	$213.31	$213.30	$213.30
Purchase #3	$45.59	4.485%	$47.6347	$47.63	$47.65	$47.60
Purchase #4	$228.81	3.377%	$236.5369	$236.54	$236.55	$236.50
Purchase #5	$145.71	4.663%	$152.5045	$152.50	$152.50	$152.50
Purchase #6	$228.50	13.109%	$258.4541	$258.45	$258.45	$258.50
Purchase #7	$163.80	3.107%	$168.8893	$168.89	$168.90	$168.90
7 purchase totals =	$1,168.39		$1,254.8858	$1,254.88	$1,254.90	$1,254.90