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	$89.79	7.850%	$96.8385	$96.84	$96.85	$96.80
Purchase #2	$147.94	11.270%	$164.6128	$164.61	$164.60	$164.60
Purchase #3	$89.37	6.258%	$94.9628	$94.96	$94.95	$95.00
Purchase #4	$75.34	3.236%	$77.778	$77.78	$77.80	$77.80
Purchase #5	$43.78	8.199%	$47.3695	$47.37	$47.35	$47.40
Purchase #6	$97.86	8.179%	$105.864	$105.86	$105.85	$105.90
Purchase #7	$140.31	12.156%	$157.3661	$157.37	$157.35	$157.40
7 purchase totals =	$684.39		$744.7917	$744.79	$744.75	$744.90