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	$216.55	8.301%	$234.5258	$234.53	$234.55	$234.50
Purchase #2	$29.35	7.414%	$31.526	$31.53	$31.55	$31.50
Purchase #3	$230.67	6.341%	$245.2968	$245.30	$245.30	$245.30
Purchase #4	$42.56	6.155%	$45.1796	$45.18	$45.20	$45.20
Purchase #5	$24.57	10.125%	$27.0577	$27.06	$27.05	$27.10
Purchase #6	$229.85	8.470%	$249.3183	$249.32	$249.30	$249.30
Purchase #7	$150.63	10.533%	$166.4959	$166.50	$166.50	$166.50
7 purchase totals =	$924.18		$999.4001	$999.42	$999.45	$999.40