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	$154.73	7.157%	$165.804	$165.80	$165.80	$165.80
Purchase #2	$155.52	6.845%	$166.1653	$166.17	$166.15	$166.20
Purchase #3	$103.73	9.431%	$113.5128	$113.51	$113.50	$113.50
Purchase #4	$145.49	7.430%	$156.2999	$156.30	$156.30	$156.30
Purchase #5	$181.33	5.365%	$191.0584	$191.06	$191.05	$191.10
Purchase #6	$223.49	3.427%	$231.149	$231.15	$231.15	$231.10
Purchase #7	$51.60	7.303%	$55.3683	$55.37	$55.35	$55.40
7 purchase totals =	$1,015.89		$1,079.3577	$1,079.36	$1,079.30	$1,079.40