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	$181.82	4.661%	$190.2946	$190.29	$190.30	$190.30
Purchase #2	$197.83	8.507%	$214.6594	$214.66	$214.65	$214.70
Purchase #3	$25.52	13.235%	$28.8976	$28.90	$28.90	$28.90
Purchase #4	$175.36	7.860%	$189.1433	$189.14	$189.15	$189.10
Purchase #5	$80.66	12.759%	$90.9514	$90.95	$90.95	$91.00
Purchase #6	$144.83	13.800%	$164.8165	$164.82	$164.80	$164.80
Purchase #7	$189.72	10.721%	$210.0599	$210.06	$210.05	$210.10
7 purchase totals =	$995.74		$1,088.8227	$1,088.82	$1,088.80	$1,088.90