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	$101.73	9.168%	$111.0566	$111.06	$111.05	$111.10
Purchase #2	$156.52	3.582%	$162.1265	$162.13	$162.15	$162.10
Purchase #3	$210.36	6.103%	$223.1983	$223.20	$223.20	$223.20
Purchase #4	$181.73	5.394%	$191.5325	$191.53	$191.55	$191.50
Purchase #5	$130.77	9.189%	$142.7865	$142.79	$142.80	$142.80
Purchase #6	$187.86	3.839%	$195.0719	$195.07	$195.05	$195.10
Purchase #7	$29.91	3.750%	$31.0316	$31.03	$31.05	$31.00
7 purchase totals =	$998.88		$1,056.8039	$1,056.81	$1,056.85	$1,056.80