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	$150.48	9.492%	$164.7636	$164.76	$164.75	$164.80
Purchase #2	$116.90	3.393%	$120.8664	$120.87	$120.85	$120.90
Purchase #3	$67.82	13.631%	$77.0645	$77.06	$77.05	$77.10
Purchase #4	$246.85	9.220%	$269.6096	$269.61	$269.60	$269.60
Purchase #5	$32.59	8.201%	$35.2627	$35.26	$35.25	$35.30
Purchase #6	$93.50	12.446%	$105.137	$105.14	$105.15	$105.10
Purchase #7	$166.59	10.379%	$183.8804	$183.88	$183.90	$183.90
7 purchase totals =	$874.73		$956.5842	$956.58	$956.55	$956.70