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	$200.36	4.543%	$209.4624	$209.46	$209.45	$209.50
Purchase #2	$146.26	12.293%	$164.2397	$164.24	$164.25	$164.20
Purchase #3	$168.50	7.412%	$180.9892	$180.99	$181.00	$181.00
Purchase #4	$196.38	11.232%	$218.4374	$218.44	$218.45	$218.40
Purchase #5	$90.71	13.312%	$102.7853	$102.79	$102.80	$102.80
Purchase #6	$129.51	6.341%	$137.7222	$137.72	$137.70	$137.70
Purchase #7	$76.47	7.784%	$82.4224	$82.42	$82.40	$82.40
7 purchase totals =	$1,008.19		$1,096.0586	$1,096.06	$1,096.05	$1,096.00