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	$156.63	5.357%	$165.0207	$165.02	$165.00	$165.00
Purchase #2	$131.96	9.494%	$144.4883	$144.49	$144.50	$144.50
Purchase #3	$120.33	4.189%	$125.3706	$125.37	$125.35	$125.40
Purchase #4	$150.30	4.435%	$156.9658	$156.97	$156.95	$157.00
Purchase #5	$103.72	7.408%	$111.4036	$111.40	$111.40	$111.40
Purchase #6	$86.29	6.123%	$91.5735	$91.57	$91.55	$91.60
Purchase #7	$184.37	13.817%	$209.8444	$209.84	$209.85	$209.80
7 purchase totals =	$933.60		$1,004.6669	$1,004.66	$1,004.60	$1,004.70