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	$139.87	3.273%	$144.4479	$144.45	$144.45	$144.40
Purchase #2	$170.88	11.755%	$190.9669	$190.97	$190.95	$191.00
Purchase #3	$86.78	12.373%	$97.5173	$97.52	$97.50	$97.50
Purchase #4	$137.84	9.686%	$151.1912	$151.19	$151.20	$151.20
Purchase #5	$171.95	8.347%	$186.3027	$186.30	$186.30	$186.30
Purchase #6	$202.78	3.746%	$210.3761	$210.38	$210.40	$210.40
Purchase #7	$68.80	3.226%	$71.0195	$71.02	$71.00	$71.00
7 purchase totals =	$978.90		$1,051.8216	$1,051.83	$1,051.80	$1,051.80