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	$148.54	6.549%	$158.2679	$158.27	$158.25	$158.30
Purchase #2	$179.69	6.605%	$191.5585	$191.56	$191.55	$191.60
Purchase #3	$64.82	13.792%	$73.76	$73.76	$73.75	$73.80
Purchase #4	$238.59	13.183%	$270.0433	$270.04	$270.05	$270.00
Purchase #5	$182.58	8.691%	$198.448	$198.45	$198.45	$198.40
Purchase #6	$214.66	6.758%	$229.1667	$229.17	$229.15	$229.20
Purchase #7	$131.81	3.801%	$136.8201	$136.82	$136.80	$136.80
7 purchase totals =	$1,160.69		$1,258.0645	$1,258.07	$1,258.00	$1,258.10