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	$59.53	3.322%	$61.5076	$61.51	$61.50	$61.50
Purchase #2	$198.52	5.564%	$209.5657	$209.57	$209.55	$209.60
Purchase #3	$51.38	7.172%	$55.065	$55.07	$55.05	$55.10
Purchase #4	$19.89	3.492%	$20.5846	$20.58	$20.60	$20.60
Purchase #5	$234.91	13.359%	$266.2916	$266.29	$266.30	$266.30
Purchase #6	$148.37	10.658%	$164.1833	$164.18	$164.20	$164.20
Purchase #7	$213.81	6.560%	$227.8359	$227.84	$227.85	$227.80
7 purchase totals =	$926.41		$1,005.0337	$1,005.04	$1,005.05	$1,005.10