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	$107.49	3.388%	$111.1318	$111.13	$111.15	$111.10
Purchase #2	$95.61	8.375%	$103.6173	$103.62	$103.60	$103.60
Purchase #3	$51.63	4.249%	$53.8238	$53.82	$53.80	$53.80
Purchase #4	$139.49	8.646%	$151.5503	$151.55	$151.55	$151.60
Purchase #5	$222.36	10.329%	$245.3276	$245.33	$245.35	$245.30
Purchase #6	$231.91	7.570%	$249.4656	$249.47	$249.45	$249.50
Purchase #7	$168.94	6.731%	$180.3114	$180.31	$180.30	$180.30
7 purchase totals =	$1,017.43		$1,095.2278	$1,095.23	$1,095.20	$1,095.20