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	$150.45	9.165%	$164.2387	$164.24	$164.25	$164.20
Purchase #2	$5.53	4.163%	$5.7602	$5.76	$5.75	$5.80
Purchase #3	$229.89	4.435%	$240.0856	$240.09	$240.10	$240.10
Purchase #4	$143.79	3.362%	$148.6242	$148.62	$148.60	$148.60
Purchase #5	$160.95	4.623%	$168.3907	$168.39	$168.40	$168.40
Purchase #6	$89.65	9.782%	$98.4196	$98.42	$98.40	$98.40
Purchase #7	$228.80	10.703%	$253.2885	$253.29	$253.30	$253.30
7 purchase totals =	$1,009.06		$1,078.8075	$1,078.81	$1,078.80	$1,078.80