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	$77.73	9.439%	$85.0669	$85.07	$85.05	$85.10
Purchase #2	$25.60	10.310%	$28.2394	$28.24	$28.25	$28.20
Purchase #3	$139.44	13.150%	$157.7764	$157.78	$157.80	$157.80
Purchase #4	$202.88	7.607%	$218.3131	$218.31	$218.30	$218.30
Purchase #5	$243.57	10.615%	$269.425	$269.43	$269.45	$269.40
Purchase #6	$130.38	6.851%	$139.3123	$139.31	$139.30	$139.30
Purchase #7	$200.83	6.754%	$214.3941	$214.39	$214.40	$214.40
7 purchase totals =	$1,020.43		$1,112.5272	$1,112.53	$1,112.55	$1,112.50