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	$86.95	4.461%	$90.8288	$90.83	$90.85	$90.80
Purchase #2	$159.82	7.388%	$171.6275	$171.63	$171.65	$171.60
Purchase #3	$125.58	4.376%	$131.0754	$131.08	$131.10	$131.10
Purchase #4	$115.69	7.137%	$123.9468	$123.95	$123.95	$123.90
Purchase #5	$188.93	10.850%	$209.4289	$209.43	$209.45	$209.40
Purchase #6	$31.62	10.791%	$35.0321	$35.03	$35.05	$35.00
Purchase #7	$107.77	10.430%	$119.0104	$119.01	$119.00	$119.00
7 purchase totals =	$816.36		$880.9499	$880.96	$881.05	$880.80