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	$45.51	3.372%	$47.0446	$47.04	$47.05	$47.00
Purchase #2	$162.25	12.826%	$183.0602	$183.06	$183.05	$183.10
Purchase #3	$5.77	3.392%	$5.9657	$5.97	$5.95	$6.00
Purchase #4	$97.61	13.720%	$111.0021	$111.00	$111.00	$111.00
Purchase #5	$214.42	10.817%	$237.6138	$237.61	$237.60	$237.60
Purchase #6	$152.66	4.650%	$159.7587	$159.76	$159.75	$159.80
Purchase #7	$78.31	4.743%	$82.0242	$82.02	$82.00	$82.00
7 purchase totals =	$756.53		$826.4693	$826.46	$826.40	$826.50