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	$198.90	8.519%	$215.8443	$215.84	$215.85	$215.80
Purchase #2	$86.40	3.652%	$89.5553	$89.56	$89.55	$89.60
Purchase #3	$131.69	5.312%	$138.6854	$138.69	$138.70	$138.70
Purchase #4	$248.37	6.179%	$263.7168	$263.72	$263.70	$263.70
Purchase #5	$60.62	5.677%	$64.0614	$64.06	$64.05	$64.10
Purchase #6	$111.43	4.112%	$116.012	$116.01	$116.00	$116.00
Purchase #7	$96.89	12.670%	$109.166	$109.17	$109.15	$109.20
7 purchase totals =	$934.30		$997.0412	$997.05	$997.00	$997.10