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	$65.95	9.661%	$72.3214	$72.32	$72.30	$72.30
Purchase #2	$246.37	4.588%	$257.6735	$257.67	$257.65	$257.70
Purchase #3	$145.73	9.488%	$159.5569	$159.56	$159.55	$159.60
Purchase #4	$31.86	3.837%	$33.0825	$33.08	$33.10	$33.10
Purchase #5	$147.86	7.463%	$158.8948	$158.89	$158.90	$158.90
Purchase #6	$131.75	9.345%	$144.062	$144.06	$144.05	$144.10
Purchase #7	$76.28	12.767%	$86.0187	$86.02	$86.00	$86.00
7 purchase totals =	$845.80		$911.6098	$911.60	$911.55	$911.70