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	$162.55	10.447%	$179.5316	$179.53	$179.55	$179.50
Purchase #2	$86.91	3.834%	$90.2421	$90.24	$90.25	$90.20
Purchase #3	$176.96	13.143%	$200.2179	$200.22	$200.20	$200.20
Purchase #4	$73.86	12.773%	$83.2941	$83.29	$83.30	$83.30
Purchase #5	$87.86	9.866%	$96.5283	$96.53	$96.55	$96.50
Purchase #6	$198.84	9.805%	$218.3363	$218.34	$218.35	$218.30
Purchase #7	$169.86	5.735%	$179.6015	$179.60	$179.60	$179.60
7 purchase totals =	$956.84		$1,047.7518	$1,047.75	$1,047.80	$1,047.60