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	$208.58	6.441%	$222.0146	$222.01	$222.00	$222.00
Purchase #2	$174.91	7.334%	$187.7379	$187.74	$187.75	$187.70
Purchase #3	$228.96	10.552%	$253.1199	$253.12	$253.10	$253.10
Purchase #4	$177.82	12.203%	$199.5194	$199.52	$199.50	$199.50
Purchase #5	$78.87	3.789%	$81.8584	$81.86	$81.85	$81.90
Purchase #6	$227.40	7.448%	$244.3368	$244.34	$244.35	$244.30
Purchase #7	$76.76	13.191%	$86.8854	$86.89	$86.90	$86.90
7 purchase totals =	$1,173.30		$1,275.4724	$1,275.48	$1,275.45	$1,275.40