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	$246.88	11.819%	$276.0587	$276.06	$276.05	$276.10
Purchase #2	$5.91	4.739%	$6.1901	$6.19	$6.20	$6.20
Purchase #3	$89.60	9.182%	$97.8271	$97.83	$97.85	$97.80
Purchase #4	$244.31	11.111%	$271.4553	$271.46	$271.45	$271.50
Purchase #5	$143.33	10.872%	$158.9128	$158.91	$158.90	$158.90
Purchase #6	$80.36	12.687%	$90.5553	$90.56	$90.55	$90.60
Purchase #7	$39.68	3.162%	$40.9347	$40.93	$40.95	$40.90
7 purchase totals =	$850.07		$941.9340	$941.94	$941.95	$942.00