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	$165.54	10.437%	$182.8174	$182.82	$182.80	$182.80
Purchase #2	$202.83	3.574%	$210.0791	$210.08	$210.10	$210.10
Purchase #3	$218.66	10.623%	$241.8883	$241.89	$241.90	$241.90
Purchase #4	$77.28	10.343%	$85.2731	$85.27	$85.25	$85.30
Purchase #5	$162.91	11.295%	$181.3107	$181.31	$181.30	$181.30
Purchase #6	$150.66	5.216%	$158.5184	$158.52	$158.50	$158.50
Purchase #7	$249.49	9.691%	$273.6681	$273.67	$273.65	$273.70
7 purchase totals =	$1,227.37		$1,333.5551	$1,333.56	$1,333.50	$1,333.60