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	$164.40	10.702%	$181.9941	$181.99	$182.00	$182.00
Purchase #2	$162.82	13.788%	$185.2696	$185.27	$185.25	$185.30
Purchase #3	$62.83	7.803%	$67.7326	$67.73	$67.75	$67.70
Purchase #4	$27.61	9.125%	$30.1294	$30.13	$30.15	$30.10
Purchase #5	$122.30	12.440%	$137.5141	$137.51	$137.50	$137.50
Purchase #6	$166.37	5.106%	$174.8649	$174.86	$174.85	$174.90
Purchase #7	$150.26	9.664%	$164.7811	$164.78	$164.80	$164.80
7 purchase totals =	$856.59		$942.2858	$942.27	$942.30	$942.30