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	$87.36	10.282%	$96.3424	$96.34	$96.35	$96.30
Purchase #2	$174.60	3.679%	$181.0235	$181.02	$181.00	$181.00
Purchase #3	$206.96	11.700%	$231.1743	$231.17	$231.15	$231.20
Purchase #4	$48.67	13.480%	$55.2307	$55.23	$55.25	$55.20
Purchase #5	$198.55	8.470%	$215.3672	$215.37	$215.35	$215.40
Purchase #6	$103.76	5.482%	$109.4481	$109.45	$109.45	$109.40
Purchase #7	$237.69	7.380%	$255.2315	$255.23	$255.25	$255.20
7 purchase totals =	$1,057.59		$1,143.8177	$1,143.81	$1,143.80	$1,143.70